MINISTRY OF TRANSPORTATION ONTARIO

BRIDGE OFFICE

STRUCTURAL STEEL COATING MANUAL

(SSCM)

2004 REVISED EDITION April 2004

To all users of this publication: The information contained herein has been carefully compiled and is believed to be accurate at the date of publication. Freedom from error, however, cannot be guaranteed. Enquires regarding the purchase and distribution of this manual should be directed to: Publications Ontario By telephone: 1-800-668-9938 By fax: (613) 566-2234 TTY: 1-800-268-7095 Online: www.publications.gov.on.ca Enquires regarding amendments, suggestions, or comments should be directed to the Ministry of Transportation at (905) 704-2065.

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FOREWORD (For the 1987 Edition - Reproduced) The Structural Steel Coating Manual, SSCM, is to be used in coating contracts prepared by the Ministry of Transportation (and Communications). It does not attempt to be an all-encompassing treatise on corrosion protection but rather addresses topics related to the needs of the Ministry. There are numerous publications that cover this subject more thoroughly and the noted references are the ones that clarify the ministry’s policies and procedures. Part 1 of the SSCM, Contract Preparation, was first issued in draft form in November 1985 and, subsequently, used in the preparation of Ministry coating contracts. After undergoing extensive revisions it is now included as part 1 of SSCM. The supplement to the SSCM, Special Provisions, was first issued in October 1985 and revised in November 1986. It is now included, with minor changes, as part 2 of the SSCM. The idea for this manual was first conceived in 1984, by Engel VanBeilen, then, Head of the Structural Office’s Field Services Section. He identified the need for a reference book on coatings for Ministry use. This manuscript is the response to that objective. The assistance of people too numerous to list in various M.T.C. offices and the Ontario painting Contractors Association who critically read and commented on the document is gratefully acknowledged. Their comments, which aided in turning an idea into reality, were reviewed and incorporated into SSCM by the following committee: R. Reel, Structural Office D. Conte, Structural Office P. Kerins, Structural Office M. Batten, Contract Management Office F. Leech, Environmental Office G. Ridley, Engineering Materials Office R. Quinn, Highway design Office We are also pleased to acknowledge the assistance of Bridge Management Section’s Anne Caravaggio, Secretary, in the numerous tasks associated with compiling and typing this manual.

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PREFACE TO THE SSCM 2004 EDITION The Structural Steel Coating Manual, SSCM, was first published in 1987 primarily to assist the ministry staff in achieving a consistent approach with respect to the preparation of coating contracts. Since then there have been five updates issued from time to time until 1992. In order to continue to meet this objective and to provide the ministry staff with the latest developments in coating technology for corrosion protection, Bridge Office recognised the need for a revised version of the SSCM. The following were assigned to work on this project: A. Coomarasamy, Senior Rehabilitation Officer, Bridge Office, ESB David Lai, Head Rehabilitation Engineer, Bridge Office, ESB There have been many developments in coating materials and practices since 1992. This revised edition incorporates many changes to the original manual, including changes made to the coating condition rating system in the OSIM, low VOC coatings, new developments & alternative approaches available for maintenance coating of steel structures such as overcoating and zone painting, details of test methods to be used during detailed coating condition survey to evaluate overcoatability of the existing coatings, a detailed discussion on criteria to be used for the selection of the most appropriate coating option, revision to the chapter on planning and a set of new specifications and special provisions. Extensive consultations with the paint manufacturers, material suppliers, contractors, consultants, ministry staff, other departments of transportation, and professional organizations, and a thorough review of the construction practices and the literature have been conducted to ensure that policies and guidelines given in the manual are based on up-to-date information. It is expected that if all involved parties are made aware of the criteria for the different maintenance coating options, latest specifications, procedures and approved coating systems, and if coating systems are applied by competent contractors under the supervision of qualified coating inspectors, it is possible to mitigate corrosion in the most economical fashion. Assistance provided by all who were contacted/consulted on this project is gratefully acknowledged. Grateful thanks are due to Grant Ridley of Materials and Engineering Research Office, Brenda Carruthers of Provincial and Environmental Planning Office, Harold Doyle of Traffic Office, and John Torontali of Bridge Office, for technical input in their respective specialised areas, and to Rita Goulet, Administrative Assistant, Bridge Office for the work associated with word processing and formatting of the document suitable for publication.

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SCOPE

Part 1of this manual details the activities essential in the planning and design of structural steel coating contracts. The text in Part I addresses four of the five main stages that contribute bridge coating, namely:

i) Assessment of the extent and location of coating breakdown and corrosion, and deciding if re-coating or other maintenance painting (touch-up, overcoating, zone painting) is required;

ii) Planning – determining the requirements for traffic control, environmental

protection and other factors, which may control or affect the contract;

iii) Design – selecting the appropriate coating system and requirements for surface preparation & cleaning; and

iv) Preparing the contract documents.

The fifth stage – construction: involving the actual surface preparation & cleaning, coating and inspection of the bridge (coating work) is outside the scope of this manual. “Construction Administration and Inspection Task Manual” prepared by the Construction Office of the Ministry, which is regularly updated, provides the necessary information related to the construction administration and inspection work of all ministry contracts. Part 2 contains typical special provisions used in coating contracts. It is to be noted that most of the technical aspects of the SP 911F06 of October 2000, SP 911S07 of October 2000, SP 911S09 of November 1999, SP 911F04 of March 1997, and SP 911 S01 “Environmental Protection During Coating of Structural Steel and Railing System” of May 1996 have been incorporated into the new OPSS 911 “ Construction Specification for Coating Structural Steel Systems” dated April 2003. Consequently, the new special provisions in Part2 of this manual are significantly smaller and deal with mainly the ‘Fill –in’ sections and aspects which were not included in the OPSS 911 of April 2003. The Special provisions 911S05 and 911S01 have also been revised by the Provincial and Environmental Planning Office to make them compatible with the new OPSS 911.

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TABLE OF CONTENTS

PART 1 - CONTRACT PREPARATION 1. INTRODUCTION ......................................................................................................... 1-1 1.1 General ........................................................................................................................................ 1-1 1.2 Coating Systems used in Ministry Structures/Bridges ................................................................ 1-1 1.3 Steel Substrate Surface Condition Requirements used for Various Coating Systems................. 1-4 2. ASSESSMENT OF EXISTING COATNG SYSTEM .................................................. 1-6 2.1 General ........................................................................................................................................ 1-6 2.2 Condition Survey of Existing Coating......................................................................................... 1-6 2.3 Coating Deterioration and Section Loss .................................................................................... 1-10 2.4 Visual Aids For Determining Coating Condition Rating .......................................................... 1-12 2.5 Other Parameters Considered for Coating Condition Rating .................................................... 1-12 2.6 Levels of Coating Failure for Maintenance Painting................................................................. 1-13 3. DETAILED CONDITION SURVEY TO EVALUATE OVERCOATABILITY OF THE

EXISTING COATING................................................................................................ 1-14 3.1 General ...................................................................................................................................... 1-14 3.2 Inspector qualification ............................................................................................................... 1-15 3.3 Inspection Tools and Materials.................................................................................................. 1-15 3.4 Visual Inspection....................................................................................................................... 1-15 3.5 Physical Inspection.................................................................................................................... 1-16 4. CRITERIA FOR RE-COATING AND OTHER MAINTENANCE PROCEDURES

FOR COATINGS ........................................................................................................ 1-24 4.1 General ...................................................................................................................................... 1-24 4.2 Full Removal and Re-Coating ................................................................................................... 1-24 4.3 Zone Painting ............................................................................................................................ 1-25 4.4 Overcoating ............................................................................................................................... 1-27 4.5 Touch-Up .................................................................................................................................. 1-32 4.6 Guide for Selection of Maintenance Painting Procedure........................................................... 1-33 5. PLANNING................................................................................................................. 1-35 5.1 General ...................................................................................................................................... 1-35 5.2 Review of Data.......................................................................................................................... 1-35 5.3 Environmental Protection.......................................................................................................... 1-37 5.4 Traffic Control and Protection................................................................................................... 1-38 6. DESIGN....................................................................................................................... 1-40 6.1 General ...................................................................................................................................... 1-40 6.2 Coating Policies and Practices of the Ministry Between 1986-1996......................................... 1-41 6.3 Current Coating Policies and Practices of the Ministry (Since 1996) ....................................... 1-41 6.4 New Steel .................................................................................................................................. 1-43 6.5 Coating of Railing Systems ....................................................................................................... 1-44 6.6 Localized Coating Failure ......................................................................................................... 1-44 6.7 Field Identification of Existing Coatings................................................................................... 1-45 6.8 Surface Preparation and Cleaning Requirements for the Approved Coating Systems .............. 1-46 6.9 Selection of the Coating System................................................................................................ 1-48 7. REFERENCES ............................................................................................................ 1-55

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LIST OF TABLES

Table 2.1 Condition Rating of Coating -Steel Railings 1-7 Table 2.2 Condition Rating of Coating -Structural Steel 1-8 Table 2.3 Rust Condition Rating Categories 1-10 Table 3.1 Criteria for Selection of Steel Structures for

Detailed Coating Condition Survey 1-14 Table 3.2 Assessment of Risk of Overcoating Based on Adhesion and Thickness of Existing Coatings 1-19 Table 3.3 Overcoating Recommendations Based on Patch Test 1-22 Table 3.4 Testing Frequencies for Various Tests During

Physical Inspection for Overcoating Projects 1-23 Table 4.1 Maintenance Coating Guide Based on Coating Condition Rating and Localities of Coating Deterioration 1-34 Table 6.1 Coating Systems and Surface Preparation Requirements 1-47 Table 6.2 Coating System Selection- Factors to be considered 1-49 Table 6.3 Advantages and Disadvantages of Coating Systems Used in Ministry projects 1-50 Table 6.4 Comparison of Coating Systems Costs –(based on 1998 to 2000 data) 1-53 Table 6.5 Coating Cost (Actual) Comparison –

Metallizing, Galvanizing and Painting 1-54

LIST OF FIGURES Figure 2.1 Rust Condition Rating Categories for Coatings in OSIM 1-9 Figure 2.2 Performance Curves of Oil/Alkyd/SSPC-SP 2 1-11 Figure 2.3 Corrosion of Base Carbon Steel 1-11 Figure 2.4 ASTM D610 Pictorial- 0.3% rust 1-13 Figure 2.5 ASTM D610 Pictorial- 10% rust 1-13

PART I - CONTRACT PREPARATION

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1. INTRODUCTION 1.1 General The Ministry of Transportation has over 700 steel bridges under its jurisdiction. A recent study1 showed that there are about 475 carbon steel bridges and about 250 atmospheric corrosion resistant (ACR) steel (or weathering steel) bridges. It is mandatory that these vital links in the highway system be protected from the detrimental effects of corrosion. ACR steel, under normal weathering cycles, oxidises to form a tough layer of rust referred to as "patina", which protects the steel from unabated corrosion2. However, this steel too is susceptible to corrosion-induced deterioration under prolonged or severe wetting and drying conditions (i.e. when the conditions are not right for the formation of patina). The corrosion-induced deterioration is aggravated in the presence of de-icing salts, especially under the leaking expansion joints and in the splash zones3, 4. Therefore, ACR steel too needs to be protected in corrosion prone areas, such as under the leaking expansion joints and in the splash zones in a bridge4. Coatings are by far the most widely used form of steel protection and corrosion control. A well-formulated coating system applied under the right environmental conditions on a properly prepared surface is expected to protect the structure for many years. Failure of the coatings invariably leads to corrosion and associated material and performance defects of steel components in the structure. The related rehabilitation and replacement costs are a concern to the ministry. Historically, coating of bridge structures has been a lower priority item in the ministry, compared to other rehabilitation needs. Due to continually rising labour costs, material costs and the enormous increase in associated environmental protection costs, it is necessary to place greater emphasis in developing economical coating alternatives in order to address the need to protect steel structures from deterioration. In recent years there have been significant developments in the areas of surface preparation methods (e.g. the use of high and ultra high pressure water-jetting), protective coating system formulations (e.g. coating systems for marginally prepared surfaces) and maintenance painting procedures (e.g. overcoating). Hence, all the currently available options for maintenance coating need to be carefully examined. 1.2 Coating Systems used in Ministry Structures/Bridges Prior knowledge of the existing coating is useful and often necessary to decide on the maintenance coating options. It is imperative to know the existing coating system, if one considers overcoating as an option for maintenance coating. The following coating systems have been used on provincial steel structures.

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1.2.1 Paint Coating Systems a) 3 Coat Alkyd System (discontinued) This system was used on most coated steel bridges until about 1974 when it was discontinued. It consisted of: - red lead primer; - Light grey second coat; - green top coat. b) High Build Alkyd System (discontinued) This system was used on most coated steel bridges from about 1974 to 1985. Its use has been discontinued. It consisted of: - yellow zinc chromate primer, one or two coats; - green high build alkyd topcoat (for hand rails); or - grey high build alkyd topcoat (for other steel work). c) Inorganic-zinc/Vinyl System (discontinued) This system was used from 1982 until the introduction of low VOC systems in 1996. It consisted of: - reddish grey to greenish grey inorganic zinc primer; - reduced vinyl wash second coat or proprietary tie coat, in white, green or grey; - green high build vinyl third coat; - high build vinyl top coat, usually grey in colour, sometimes green. d) Epoxy-Zinc/Vinyl System (discontinued) This system was used on coated steel bridges starting in 1987 until the introduction of low VOC systems in 1996. It consisted of: - green or reddish grey organic zinc primer; - high build vinyl second coat, in green or light grey; - high build vinyl topcoat, grey in colour. e) Aluminum-Filled Epoxymastic System (discontinued) This system had been used since about 1982 on a number of coated steel bridges. It had also been used in selected locations on atmospheric corrosion resistant (weathering) steel, under expansion joints. It was discontinued in 1988 as a complete recoating system, but could still be used for touch-up. It consisted of: - two coats of aluminum coloured epoxymastic.

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f) Coal Tar Epoxy (System 5) This system has been used in the past on the inside of some box girders. It is black or dark brown in colour. g) Inorganic-Zinc/Epoxy/Urethane System (System 4) This system is one of the low VOC systems that have been in use for coating structural steel since 1996. It consists of: - reddish grey to greenish grey inorganic zinc primer; - an epoxy second coat, green or white; - urethane top coat, grey in colour. h) Epoxy-Zinc/Epoxy/Urethane System (System 2) This system is one of the low VOC systems that have been in use for coating structural steel since 1996. It consists of: - green or reddish grey organic zinc primer - an epoxy second coat, green or white; - urethane top coat, grey in colour ( for ACR Steel brown in colour). i) Inorganic Zinc/Acrylic/Acrylic (System 3) This system is one of the low VOC systems that are in the DSM list for coating structural steel. It has only been used on a trial basis on some girders of Willow Creek Bridge. It consists of: - greenish grey inorganic zinc primer; - buff acrylic mid coat; - grey acrylic topcoat. j) Epoxy-Zinc/Acrylic/Acrylic (System 1) This system is one of the low VOC systems that are in the DSM list for coating structural steel. This system has only been used on a trial basis on some girders of Willow Creek Bridge. It consists of: - greenish grey organic(epoxy) zinc primer; - buff acrylic mid coat;

- grey acrylic topcoat.

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k) Overcoating Systems Paint coating systems recommended for marginally prepared surfaces, as defined in OPSS 17045, are referred here as Overcoating Systems. Two coating systems were approved in 19986, based on MTO laboratory evaluation. In the years 2001 and 2002, overcoating was used for coating of the external girders of Moira River Bridge, under contract # 2000-0076. The prime coat is an aluminium filled epoxy mastic type product, the mid coat is high solids flexible aliphatic surface tolerant polyurethane and the topcoat is aliphatic polyurethane. This system was applied on to the north side of the bridge. However, due to the non-availability of the mid coat material, the south side received two coats of aluminium filled epoxy mastic prime coat material and aliphatic polyurethane topcoat. This bridge was previously painted with high build alkyd system [see subsection (b) above], which received the above overcoating treatment. 1.2.2 Hot–Dipped Galvanizing Hot-dipped galvanizing of steel hand rails components commenced in 1987, after the introduction of a coating policy which required that standard steel hand rails be hot-dip galvanized and the posts and brackets metallized (see Appendix IV). Hot-dipped galvanizing was used for coating of five bridges during 90’s, which included Upper Canada CNR Overhead in the Eastern Region, Cripple Creek Bridge, New Liskeard, and CNR Overhead at Parry Sound (Site # 44-163 - now a Municipal Bridge) in Northern Region, Dereham Townline Overpass and Kent County Road # 15 Bridge over Hwy 401, in the South Western Region1. 1.2.3 Metallizing As stated above, metallizing of steel posts and brackets commenced in the year 1987 as a field application method using flame spray process. Thermal arc sprayed metallizing was employed for coating of the girders and new diaphragms of Division Street overpass, Hwy 401, Kingston in 19987. A clear seal coat was applied over the metallic coating to provide additional corrosion (barrier) protection. This work was done off site in a shop and the coated components were transported back to the site and erected prior to the installation of a new bridge deck. 1.3 Steel Substrate Surface Condition Requirements used for Various

Coating Systems The alkyd systems and aluminium epoxymastic system used in the past were applied onto steel surfaces abrasive blast cleaned to SSPC -SP6/NACE No. 3 Commercial Blast standard8 with the exception of a few structures which were coated over mill scale. For the vinyl systems and the Low VOC systems, specification required the steel surfaces to be abrasive blast cleaned to SSPC-SP10/NACE No. 2, Near-White Metal Standard9. For the metallizing of steel girders of Division Street overpass in Kingston, the specification

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called for the steel surface to be abrasive blast cleaned to SSPC SP-5/NACE No.1 White Metal standard10 having a surface profile within a range of 50-100 microns. At present, as a general practice, only the low VOC three coat paint systems from the Designated Sources Materials (DSM) 12 list are specified for coating application on abrasive blast cleaned steel.

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2. ASSESSMENT OF EXISTING COATNG SYSTEM 2.1 General Prior to any field inspection, all available documents concerning the original coating and subsequent maintenance coating and their respective performances must be studied. This review will establish what the inspector may encounter and also what to look for. While conducting the detailed visual inspection, the Regional Structural Section should note the coating condition as well as the condition of the members of the structure. 2.2 Condition Survey of Existing Coating 2.2.1 General A structure must be inspected prior to contract design to ascertain the type and condition of the existing coating system, condition of structural steel members and to assess problem areas and maintenance requirements such as: - corrosion perforated steelwork that may need strengthening or replacement prior to

coating; - deck drains and/or 25mm drain tubes that should be lengthened to prevent deposition of runoff water on freshly coated steel members; - potential access problems that may necessitate diaphragm removal at abutments or piers in order to clean and coat the main steelwork; - bearings requiring protection measures prior to sandblasting; - expansion joints that should be repaired or replaced ,or eliminated to prevent

deposition of runoff water on freshly coated steel members; and, - to decide on maintenance painting options such as zone painting, touch up, full

removal & recoating and to decide on conducting a detailed coating condition survey to assess overcoatability of the existing coatings.

2.2.2 Biennial Inspection and Coating Condition Rating System The biennial inspection of existing coating is addressed in Ontario Structure Inspection Manual, OSIM 12.The coating condition rating has been recently revised in the OSIM in order to be consistent with the new Ontario Bridge Management System (OBMS).

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Instead of the six categories of performance and material rating in the previous system, the new system in the OSIM has the following four condition ratings: Excellent, Good, Fair and Poor. This change is necessary to have a unified system for rating all the different components in a structure and it facilitates the quantifying of percentage of each component in each of the condition states. The new condition rating in OSIM for coatings is based on material defects and Rust Condition Rating Categories 1-4, which is described below and illustrated in Figure 2.1 This rating is performed for a component or sections of a component when there is a wide variation in localised areas of a component. The new OSIM Coating Condition Rating Categories and the parameters used for this assessment are presented in Table 2.1 and Table 2.2. As shown in Table 2.2, condition rating of coatings on substructures and superstructures is dependent on rust condition rating category as well as on the extent of other coating defects (such as checking, cracking, alligatoring, undercutting, pinholing, runs, sags, overspray, blisters, chalking, intercoat delamination, peeling, underfilm corrosion, pinpoint rusting, bridging, edge defects, shadows etc.). Rust condition rating in the new OSIM (Tables 2.1 & 2.2) is based on the percentage of surface rust on the coated steel. ASTM D 610 standards/sketches13 and SSPC VIS 2 Pictorial standards14 are used as guides for rating purposes. The rust condition rating categories and maximum % rust for various categories are given in Table 2.3. This evaluation is performed by detailed visual inspection of coatings on steel elements and the results of the inspection are expressed in percentage of the total area of each element. The results are then fed into the Bridge Management System (BMS), which in turn will indicate whether a detailed coating condition survey (for assessing overcoatability) is warranted. The threshold value for the BMS program to trigger such a detailed coating condition survey is when the combined area in Fair and Poor conditions is >25 % of the area, but the area in poor condition should be less than 10%.

Table 2.1

Condition Rating of Coating* – Steel Railings Excellent Condition Good Condition Fair Condition Poor Condition RUST CONDITION** RATING CAT.1

RUST CONDTION RATING CAT.2

RUST CONDITION RATING CAT.3

RUST CONDITION RATING CAT. 4

Table 2.2

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Condition Rating of Coating* - Structural Steel Substructures and Superstructures

Excellent Condition Good Condition Fair Condition Poor Condition No Observed Material Defects

Minor Checking, Cracking, Alligatoring, Chalking

Checking, Cracking, Alligatoring

Severe Checking, Cracking, Alligatoring

Intercoat Delamination, Peeling (top coat only)

Undercutting, Blisters, Peeling (prime coat), Underfilm Corrosion

Signs of Chemical Attack

Overspray, Runs, Sags, Pinholing

Bridging, Edge Defects, Shadows, Pinpoint Rusting

RUST CONDITION** RATING CAT.1

RUST CONDITION ** RATING CAT.2

RUST CONDITION ** RATING CAT.3

RUST CONDITION ** RATING CAT. 4

Detailed Coating Condition Survey if >25% of combined area in Fair and Poor Condition States, and the area of Poor Condition state is < 10%***

Detailed Coating Condition Survey if >25% of combined area in Fair and Poor Condition States, and the area of Poor Condition state is < 10%***

* Galvanized elements are included under the “Coating” category. ** OSIM Rust Condition Ratings based on ASTM D 610 sketches are shown in

Figure 2.1. *** In order to consider overcoating as a viable rehabilitation option, a detailed

condition survey should be triggered before deterioration is too widespread.

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Category 1: No Rust Condition State: Excellent Category 2: Light Surface Rust Condition State: Good Upper limit 1% rust shown Category 3: Medium Surface Rust Condition State: Fair Upper limit 3% rust shown Category 4: Severe Surface Rust Condition State: Poor 5% rust shown as example Figure 2.1: Rust Condition Rating Categories for Coatings in OSIM

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Table 2.3

Rust Condition Rating Categories % Rust Rust Condition Rating

Category No rust CAT. 1

0 -1 CAT. 2

1 -3 CAT. 3

Greater than 3 CAT. 4

Detailed condition survey of the coating is necessary if overcoating is to be considered. Refer to Section 3.0. The use of a pen knife to lift the paint film from areas which surround total loss of coating will assist in determining the actual area, which should be considered as failed, resulting in more appropriate rating. During detailed coating condition survey, the percentage of metal area exposed or affected by corrosion and corrosion by-products as evident on the steel surface is also evaluated to determine the sectional loss of a component or a sectional loss in localized areas. 2.3 Coating Deterioration and Section Loss Although a coating's breakdown may be insignificant when first inspected, this deterioration is ongoing with a linear increase around the 0.1% - 0.3% of surface rust mark15. If coating repairs are delayed unduly, then the damaged area will most likely be much greater when re-coating is done in subsequent years. Figure 2.2 and 2.3 show how rapidly coatings can deteriorate if not maintained and how this then translates into section loss16.

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Figure 2.2: Performance Curves of Figure 2.3: Corrosion of Oil/Alkyd/SSPC-SP 2 Base Carbon Steel

Figure 2.2 is for an oil/alkyd coating but similar curves were reported for other coatings in different environments. The points A, B, C refer respectively to 0.03%, 0.1% and 0.3% rust 16. The graph shows that at about 0.3% rust the coating breakdown accelerates rapidly. Figure 2.3 shows the rate of metal loss after the coating has deteriorated completely. The SSPC has determined that metal loss may occur beyond the 10% rust mark16. In the new OSIM coating condition rating, rust marks of 3% and above are rated as in Poor condition. The Metals Handbook17 by the American Society for Metals (ASM) cautions that the environmental classifications into rural, urban, industrial, marine, etc., are gross oversimplifications of a particular situation. It suggests that the corrosion rate data, like the above shown in Figures 2.2 and 2.3, should be used as qualitative rather than quantitative. Corrosion rates can vary considerably within small proximities. The main factors affecting corrosion of bridge members in Ontario and other places where de-icing salts are used for winter maintenance are: a) the degree of exposure to de-icing salts and b) the duration of wetness. The Ministry’s experience clearly shows that within a bridge there can be different corrosive environments. Under leaking expansion joints, at locations subject to salt splashing, and in areas where there is bird droppings and accumulation debris, steel components are in a severe corrosion environment and corrosion can occur at higher rates. Areas that are not exposed to salt spray or the accumulation of debris and moisture usually show much lower corrosion rates and can be considered as relatively benign. Therefore, during inspection, special attention needs to be placed to the corrosion prone areas described above to assess the extent and degree of coating failure and corrosion damage.

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2.4 Visual Aids For Determining Coating Condition Rating The OSIM condition rating for coating is determined by assessing the degree of rusting (Rust Condition Rating Categories) and other defects included in the Table 2.2. To assist the person conducting the assessment arrive at an objective Rust Condition Rating Category (and Coating Condition Rating), the following sketches in Figures 2.1, based on the ASTM D 61013 should be used. These sketches are visual aids and they compare, where applicable, the rust condition ratings for painted steel components to pictorial representations of percent rust in SSPC- VIS 214 published by the SSPC. The SSPC-VIS 2 pictorials are representative of rust but not blisters. Blisters should be treated as if they were rust when determining the rust condition rating. 2.5 Other Parameters Considered for Coating Condition Rating In addition to the assessment of degree of rusting (Rust Condition Rating), the inspector should look for and assess the following defects in the coating. Formulation/Material related Defects:

-Checking -Cracking

-Alligatoring -Chalking Adhesion Related Defects: -Intercoat Delamination

- Peeling (top coat only) - Undercutting

- Blisters - Underfilm Corrosion Defects related to External Factors: -Signs of chemical attack Application related defects: -Overspray -Runs, Sags -Pinholes,

-Pinpoint rusting -Bridging

-Edge defects -Shadows Detailed description on the above defects and their causes are found in the Steel Structures Painting Manual Volume 1, Good Painting Practice18and Corrosion Prevention by Protective Coatings19.

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2.6 Levels of Coating Failure for Maintenance Painting MTO does not wait for a fixed time period before re-coating and maintenance painting. The current practice is to allow certain level of corrosion or coating failure to occur before re-coating or to adopt other maintenance painting procedures. For many years, the Ministry has been using 10% rust mark (based on ASTM D610, SSPC-VIS 2) as a failure point of the existing coating for primary components that requires re-coating. With the revision of the OSIM coating rating categories, areas of components exhibiting 3% rust mark and above are all classified as in Poor Condition. Many organizations use more stringent criteria than the ministry's criteria for re-coating. The Society for Protective Coatings, SSPC, criterion falls between 0.03% - 0.3% rust16 (see Figure 2.4) while the British Iron ands Steel research association use 0.1% rust (ref. 19, p 294). Appleman 16 says a structure should be re-coated at least at the 10% rust mark (see Figure 2.5) before there is a possibility of metal loss, which is seen as happening beyond the 10% rust mark.

Figure 2.4: ASTM D610 Pictorial- 0.3% rust

Figure 2.5: ASTM D610 Pictorial- 10% rust

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3. DETAILED CONDITION SURVEY TO EVALUATE OVERCOATABILITY OF THE EXISTING COATING

3.1 General A detailed coating condition survey is carried out to assess whether the structure is a suitable candidate for overcoating project and to assess the risks associated with such a decision. In order to select candidate structures for such a survey, one has to consider not only the coating condition rating of individual structural elements, but also about the overall coating condition (of all the elements) of the bridge structure. In the case of steel girders, the ends of girders are considered as separate elements from the rest of the girders12. The following combinations of coating condition rating is proposed for the selection of structures for detailed condition survey and to assess whether the structure is suitable for overcoating (Table 3.1). Since the detailed coating condition survey to evaluate overcoatability is discussed in detail in this section of this manual, OSIM only lists the tests to be performed during a detailed coating condition survey and makes reference to this manual (Structural steel coating manual) in Section 1.3.3 – Specialized Investigations. The detailed coating condition survey for assessing overcoatability of the structure includes visual inspection and physical inspection of the structure and the existing coating, which is discussed in depth below in this section – (Section 3).

Table 3.1 Criteria for Selection of Steel Structures for Detailed Coating Condition Survey

Ends of Girder Middle Section of Girder b Overall Category

% Area in Fair & Poor Condition a

% Area in Good & Excellent Condition

% Area in Fair & Poor Condition a

% Area in Good & Excellent Condition

Action Option/ Comments

A

50> X >25

> 50

50> X >25

> 50

Detailed coating Condition survey and technical assessment for overcoating

Overcoating may be an option

B

> 50

< 50

50> X >25

> 50

No immediate action required, if length of girder is <20 m

Overcoating may be an option for girders > 20m

C 50> X >25

>50

<25

>75

No action required at present

Overcoating may be an option in the future

Note: If majority of the girders in the structure comes under the overall category A and the rest in category C, it is recommended that a detailed coating condition survey is carried out to assess the technical suitability of the structure for overcoating, provided that the area of poor condition is under 10%. However if the majority of the girders are in category C, with a smaller number in category A, the detailed coating condition survey may be delayed. Superscript a: % of Poor Condition should be <10%; Superscript b: Criteria to be used for full girders, if the ends of the girders are not rated separately.

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3.2 Inspector qualification The inspector performing a detailed coating condition survey should have: i) Passed NACE Level I Coating Inspector Training; and, ii) 3 years of coating inspection experience. 3.3 Inspection Tools and Materials The following is a list of equipment required for a detailed coating inspection: 1. Inspection mirror, torchlight, 30X magnifying glass, preferably an illuminated type. 2. Knife (putty knife) sample bags and vials. 3. Camera with close up lens and appropriate quantity of film or a digital camera. 4. Constant Pressure- Probe Type II Dry Film Thickness (DFT) gauge and

calibration standards - to determine total DFT of coating. 5. Tooke gauge - to determine total DFT and DFT of individual coats/layers. 6. Coating adhesion testing based on ASTM D3359 (or a Modified Procedure B

based on ASTM D 3359 for the use of KTA-Tator Cross Cut Guide and accessories for adhesion testing is given subsequently).

7. Equipment for pull-off adhesion testing conforming to ASTM D 454120 (Note: Of the three types of apparatus, the hydraulic and pneumatic testers (e.g. PosiTest Pull-off Adhesion Tester, HATE & PATI) give more accurate pull-off adhesion values compared to the hand operated mechanical tester such as Elcometer 106).

8. Zinc rich touch-up paint21 for repair of areas where destructive tests (such as Took gauge DFT measurements, cross hatch adhesion test and pull-off adhesion tests etc.) were conducted.

9. Soluble salt test kits (e.g. KTA Swab test kit, Bresle Patch test kit, Chlor*Test kit for extraction and quantitative estimation of chloride ions; Available from KTA- Tator, Atlas International and Termarust Technologies). 10. Personal protective equipment. 3.4 Visual Inspection Visual inspection to be performed during a detailed coating condition survey requires a much closer examination of the structure compared to the initial biennial inspection, which triggered the detailed inspection. It is more comprehensive and quantitative with regard to reporting of the coating condition of all the elements and the structure as a whole. The coating condition rating is based on New OSIM Table 4 for Coating - Structural Steel Substructures and Superstructures. In this survey, special attention should be paid to the recording of the percentage of each level of failure accurately with respect to the percentage area of each element. Each individual girder or truss should be rated separately. The results of this survey should be compared with the previous biennial inspection report, (to check the differences and discrepancies, if any) and to evaluate the progress of the coating deterioration, especially when there is a significant time lag between the previous inspection and the detailed inspection.

April 2004 1-16

3.5 Physical Inspection 3.5.1 General Physical inspection of the existing coating is conducted to determine the dry film thickness (DFT), number of layers of paint, adhesion, underlying substrate condition, coating type and the presence of soluble salt and other surface contamination. The number of test locations examined must be such that it provides a representative picture of all major conditions existing on the structure22. Table 3.4 gives testing frequencies for the different tests. Prior to the detailed inspection, the inspection crew should review all the information available with regard to the structure and the existing coating, including the previous construction and inspection reports. Information on the coating materials and the abrasive blast cleaning standard used for coating work could be obtained from the above reports. Section 1.2 of this manual also gives valuable information regarding various coating systems and surface preparation standards used over the years on ministry structures, which may be of use if information with regard to coating systems are not available from other sources. However, laboratory testing of the coating material is necessary for positive identification of the coating materials/systems. For such a positive identification of the existing coating, small representative paint chips (small paint samples) retrieved from the structure should be sent to the Concrete Section of the Materials Engineering and Research Office (MERO) of the MTO, 2nd Floor, Building C, 1201 Wilson Avenue, Downsview, Ontario. 3.5.2 Dry Film Thickness (DFT) Measurements DFT measurements to determine the total DFT of the existing coatings can be readily performed using a Type 2 (constant pressure probe) magnetic gauge (such as Positector 6000 etc.). It is recommended that DFT measurements be taken on all accessible faces of the steel girders/members. Since many potential candidate MTO steel structures for overcoating projects consist of I-beam carbon steel girders, it is appropriate that DFT measurements are taken, possibly on all the accessible faces of the I-beam girders in the structure, i.e. on 7 faces. Ray Weaver of SSPC, Pittsburgh, in his answer to Problem Solving Forum on Measuring DFT on Steel I-Beams23, states that SSPC is developing a procedure for measuring the dry film thickness of coatings on steel beams. The following procedure, which was suggested by Mr. Weaver as a possible procedure for measuring DFT on I-beams, is recommended for conducting DFT measurements using Type II magnetic gauge on MTO structures with I-beam girders (for overcoating projects).

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3.5.2.1 Procedure for Measuring DFT on Steel I-Beams For beams up to 12 m in length, choose a 0.6m length of beam near one end and another 0.6m length near the centre. As indicated in SSPC-PA 2 (Section 4.1.2), take one spot measurement on each of the seven surfaces within the designated 0.6m length. The average of these spot measurements is the DFT. If some of the seven surfaces are not accessible, take at least five spot measurements with at least one spot on each accessible surface. Repeat for the other 0.6m length. For beams between 12m and 24 m in length, divide the beam into thirds. Choose a 0.6m length of beam near one end, and randomly select a 0.6m length from each of the other thirds. Measure the DFT in each 0.6m length as described above. For beams over 24 m in length, divide the beam into 12m segments. The final segment will be less than 12m, if the total length is not a whole number of 12m increments. Choose a 0.6m length near one end and randomly selected 0.6m length from each beam segment. Measure DFT in each 0.6m length as described above. 3.5.2.2 DFT of Individual Layers DFT of individual layers and the number of layers on coated steel can be measured using a Tooke gauge. The procedure is based on ASTM D 413824, “Measurement of Dry Film Thickness of Protective coating Systems by Destructive Means”. Tooke gauge measurements are made by making a sharp straight scribe/cut at precise angle through the paint layers down to the substrate, using the cutting tool that comes with the instrument. The scribe is viewed through a 50x microscope of the instrument and the number of each coat and thickness of each coat are measured. When examining the coating, the inspector can observe the condition of the substrate as well. If rust is present beneath the primer coating, it will often be visible. Since this is a destructive test method, the damage caused to the coating has to be repaired after taking the measurements. 3.5.3 Coating Brittleness One method for assessing the condition of the coating in terms of its flexibility (or brittleness) is to scrape off a small area of paint with a sharp carpenter’s chisel. If the paint film curls up, it is flexible and in good condition for overcoating with little risk. If the film fractures into chips, it is considered brittle and a higher risk for overcoating25. Coating brittleness can also be assessed by a simple crosscut of the coating film by a sharp knife. Poor coatings tend to crack and flake/come off, especially at the intersection of the cuts. Again this is a destructive test and the coating has to be repaired after the test. 3.5.4 Surface Contaminants Ionic surface contaminants such as chlorides and sulphates can lead to decreased coating life and increased rate of corrosion of the substrate, whereas grease, oil, and dust result in poor wetting and adhesion of the overcoating system. Quantitative methods and semi-

April 2004 1-18

quantitative methods such as swab tests (SSPC methods or ISO methods26) are available for the measurement of soluble salts such as chlorides and sulphates. Since de-icing chemicals/salts are used in most of the highways and bridges, chloride ion would be the most widely expected invisible soluble ionic contaminant in bridge structures. As such, it is recommended that a quantitative measurement of soluble chlorides on the surface of the steel members be conducted using one of the commercially available kits (e.g. Bresle Patch 27, CHLOR*Test28, KTA- Tator Swab test29), during detailed inspection for overcoating projects. The details of the field methods for retrieval and analysis of soluble salts on substrates are given in SSPC-TU 430 and other SSPC publications 31, 32. Recent publication33 based on the work done by Federal Highway Administration (FHWA) and Soil and Land Use Technology Inc., provides some guidelines and recommendations for performing chloride extractions from salt contaminated substrates using commercially available kits and for quantitative estimation of chloride ions in the extracted solution. Tests to determine the extent of contamination (contamination level) with grease, oil and dust may also be conducted using published methods 32 during the detailed inspection. It is necessary to record exactly the locations of sampling and the procedures adopted for sampling and testing of contaminants. 3.5.5 Coating Adhesion 3.5.5.1 Adhesion Test based on ASTM D 335934 (Modified Method B Cross-

Hatch Test Method) The minimum specified thickness of coating systems used in MTO structures is expected to be above 200 µm (or above the minimum specified) at the time of application. In order to evaluate adhesion of these coatings, it is recommended that a modified version35 of ASTM D 3359 Method B, called crosshatch method, be used. This modified procedure requires the spacing of 5mm between adjacent cuts. KTA-Tator crosshatch cutting kit (steel template with the required spacings, sharp razor or knife, pressure-sensitive adhesive tape) or equivalent apparatus could be used. A grid of cuts is made through all paint layers (by first making a set of parallel cuts using the cutting tool with a spacing of 5mm between the cutting edges and then making a second series of cuts, made perpendicular to the first), resulting in 9 squares each 5mmx5mm. Pressure-sensitive tape is applied to the cut surface and pulled off as given in the ASTM D 3359 Procedure34. The amount of paint removal within the grid is used to assess the strength of the adhesive bond. On a scale of 0B to 5B, Rating of 1B is between 35% and 65% paint removal, which is unsatisfactory. Rating of 2 B is 16% to 35%, which is considered marginal, with a considerable risk, since overcoating this paint would result in early failure. Ratings of 3B, 4B and 5B are satisfactory indicating that the old paint is sound enough to be overcoated with compatible coating system and would have the normal expected life. Risk assessment for overcoating based on ASTM D 3359 adhesion tests and coatings thickness1 are summarized in Table 3.2. ASTM D 3359 Method B can be directly applied (unmodified) for coatings having a thickness of <125µm.

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Table 3.2 Assessment of Risk of Overcoating Based on Adhesion and Thickness of Existing

Coatings Adhesion Classification, ASTM Method D3359 (Amount of paint removed)

Overcoatability and Associated Risks

Method B, using 5mm* guide to

make cross-hatch cut

Method A

x-cut method

<125µm 125 - 200µm 200 -500µm >500µm

5B (None) 5A O.K - No risk O.K - No risk O.K - No risk O.K. - No risk

4B (1% - 5%) 4A O.K - No risk O.K - No risk O.K. - No risk O.K. - No risk

3B (6 %- 15%) 3A O.K - No risk O.K - No risk O.K. - No risk O.K, Low risk

2B (16% -35%) 2A Low risk Low risk Low risk Low - Medium risk

1B (36%-65%) 1A Medium risk Medium risk Medium risk High risk

0B (> 65%) 0A Do not overcoat

Do not overcoat

Do not overcoat

Do not overcoat

* Crosshatch cutting using 5mm guide is a modified procedure developed by KTA Tator to evaluate adhesion of thicker coatings (>125µm) by method B of ASTM D 3359.

For coatings <125µm, ASTM D 3359 Procedure B (unmodified) can be applied. 3.5.5.2 Pull-Off Adhesion Test As an alternative to the adhesion testing based on ASTM D3359, pull-off adhesion tests based on ASTM D 454120 can be carried out to assess the adhesion of the aged coatings. According to KTA Tator Report35, “In a survey of SSPC Paint manufacturers, minimum values of 0.34 MPa - 2.1 MPa (50 –300 psi), were cited as necessary for overcoating. Lenhart and El-Nagger have suggested the pull-off adhesion values of 0.69 MPa - 1.38 MPa (100 -200 psi) are marginal for overcoating and that adhesion of 1.72 MPa – 4.14 MPa (250 -600 psi) is acceptable for overcoating”. Glen Amos, in a recent article36 on “Maintenance Painting/Practical Advice”, states, “As a rule, if the new coating is a single component product that would add very little stress to the old coating, a minimum of 1.38 MPa – 1.72 MPa (200 - 250 psi) adhesion/cohesion is acceptable. Conversely, if the new coating is a multiple-component product that would impart significant stress during cure, the old system should display minimum adhesion/cohesion readings of 2.4 MPa (350 psi). This higher number is also appropriate for structures with more than five coats of old paint, >20 mils (508 µm) thickness of old paint, and a severe environment”. Based on the above information, it is recommended that a pull-off adhesion value of over 1.38 MPa (200 psi) is required for overcoating projects.

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There is a significant scatter (margin of error) in pull-off adhesion values when mechanical testing devices (such as Elcometer 106) are used. Therefore, caution should be exercised when pull-off adhesion values are considered for making decisions. More consistent/accurate pull-off adhesion values are usually expected with pneumatic and hydraulic instruments (such as the PATI, HATE, PosiTest Pull-Off Adhesion Tester). All the pull-off adhesion test methods require metallic (aluminum) dollies of a specific size to be glued on to the surface of the coatings to conduct the test. It has been found that the some of the 5-minute cure epoxy compounds and cyano-acrylate adhesives may not be suitable to securely bond the test dollies onto the coatings (for the pull-off adhesion test) and in general the epoxies with 24 hour curing period are suitable. However Lepage’s 5-minute epoxy glue was found to be satisfactory after a curing period of 2-3 hours. Lord 201 acrylic adhesive with Lord Accelerator 4 (available from Lord Corporation) was also found to give satisfactory bonding of the dollies with a curing period of 2 hours, which enabled the pull-off adhesion test to be completed on the same day. 3.5.6 Patch Test Patch testing is a good method for determining whether the new overcoating system that is to be used is compatible with the existing coating. The test should be performed so that the worst-case exposure to the patch is achieved. This could be conducted as described in ASTM D 506437. Representative areas or components of the structure should be selected for testing. It is important that any test patch should include the feathered edges of the existing paint at prepared rusted or degraded areas. Area(s) in poor condition as well as area (s) that typify the overall condition of the existing coating should be selected for this evaluation. The areas selected should be inspected (visual and physical) carefully and the results of the inspection recorded. It is recommended that the surface preparation to be used for the patch test should be the same as the procedure to be used for overcoating project and is as follows: a) SSPC-SP 1- Solvent Cleaning38 to remove oil residues and patches. b) SSPC-SP 11 -Power Tool Cleaning to Bare Metal40, of rust spots larger than100cm2. d) Power washing with potable water at 10.34 MPa – 17.24 MPa (1500 - 2500 psi) pressure. e) Blow dry with contaminant free compressed air. Overcoating materials to be used for patch testing should be from the MTO approved coating systems for marginally prepared coated steel. It is necessary to apply the overcoating materials by the same procedure that will be used on the overcoating project, at the recommended thickness under the recommended atmospheric and surface conditions. The patch shall be re-inspected after curing/drying and condition of the patch shall be documented. If the old coating is attacked, there will be signs of softening, blistering or delamination. If there are no signs of initial failure then, the test patches should be re-inspected a second time after 6 -12 months, preferably after one winter season. DFT measurements and adhesion test may be conducted on the patch. Patch test results are rather straightforward to interpret. Good compatibility is indicated by the absence of any delamination in the patch or adhesion failures. Delaminated

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patches imply a very high risk. Poor intercoat and or substrate adhesion indicates that there is intermediate level of risk associated with overcoating. Signs of early rusting or blistering may also indicate a higher risk associated with overcoating. Other warning signs include wrinkling, mud cracking and lifting1. Recommendations for feasibility of overcoating based on patch testing are given in Table 3.3. 3.5.7 Compatibility Data At present the ministry does not have any specific information with regard to compatibility of approved overcoating materials with the existing coating systems on MTO bridges. Therefore, it is mandatory at the initial phase to conduct patch testing with the approved overcoating materials on to the following existing coating systems on MTO bridges: -Old Alkyd system with red lead primer -Alkyd system with zinc chromate primer -Vinyl systems with inorganic zinc and epoxy zinc -Low VOC epoxy zinc/epoxy/polyurethane -Low VOC inorganic zinc/epoxy/polyurethane Once the data on compatibility of the approved overcoating systems (materials) with the above existing coating systems are collected and analysed, this information could be made available for future reference.

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Table 3.3

Overcoating Recommendations Based on Patch Test

Observation/Test results* Inspection Tools/Method Recommendations/ Comments

Patch in good condition without any visible signs of delamination, peeling, signs of rusting or other failures

Visual, Observation of the surface under x30 magnification Meets adhesion test requirements

Good compatibility (material compatibility) - System used on the patch is suitable for overcoating

Delamination of the patch Visual, observation of the surface under x30 magnification

Very poor compatibility- Overcoating is not recommended

Poor intercoat and or substrate adhesion on visual observation or on adhesion testing

Visual, observation of the surface under x30 magnification. Do not meet the adhesion test requirements

Poor compatibility- Overcoating is not recommended

Rusting and blistering Visual & observation under X30 magnification

Effectiveness in reducing the corrosion rate is poor. - Not satisfactory for overcoating

Wrinkling, mud cracking, lifting, peeling

Visual & observation under X30 magnification

Poor compatibility- Overcoating is not recommended

* After a minimum of 6 months service exposure & through one winter.

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Table 3.4

Testing Frequencies for Various Tests During Physical Inspection for Overcoating Projects

TEST Location/Location Selection Number of Tests Recommended

Total DFT (Type II Pull-off magnetic gauge)

In Conformance with SSPC-PA 2

In Conformance with SSPC-PA 2

DFT of individual layers by Tooke gauge

Select at random (or select areas where the total DFT from the previous measurements are either too low or too high)

Limit the number to a few tests at representative locations

Coating Brittleness Select at random, to include areas where the coating is prone to more environmental degradation (e.g. external faces of girders, splash zones, areas close to leaking expansion joints etc.)

Limit the number to a few tests at representative locations

Surface Contaminants- Soluble chloride

Select areas close to expansion joints, splash zones as well as areas where there is less likelihood of salt contamination

A few representative locations (about 5- 9 tests)

Surface Contaminants- Dirt

Random A few representative locations

Surface Contaminants- Oil and grease

Select locations after careful visual observation- Splash zones, external girders etc.

A few representative locations

Adhesion- Cross-hatch method

Select areas close to expansion joints/ends of girders, external girder web and lower flange as well as some representative inner sections of steel members

A few representative locations (This test need not be carried out if pull-off adhesion test at representative location is carried out)

Adhesion- Pull-off adhesion test

Select areas close to expansion joints/ends of girders, external girder web and lower flange as well as some representative inner sections of steel members

A few representative locations

Patch test Only done if all the other test results are satisfactory to consider overcoating as an option for maintenance painting and when compatibility data is not available for the systems concerned.

A few representative locations (e.g. external girder web, areas close to the expansion joints, areas where high or low DFT recorded etc.

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4. CRITERIA FOR RE-COATING AND OTHER MAINTENANCE PROCEDURES FOR COATINGS

4.1 General The primary reason for coating steel is to prevent loss of a section with a secondary function of maintaining the aesthetics of the structure. With the change in the Ministry's role from hands-on delivery work to steering, it is expected that most of the coating related work would be done by contract work as part of the capital program, while little touch-up work would be done by the Districts. However, it is economically advantageous to touch-up coatings in critical areas before serious coating deterioration or corrosion occurs. Despite the funding and service delivery model, the following coating options are available: • Full removal and re-coating • Zone painting • Overcoating • Touch-up The prime factor to be considered for the selection of the most suitable coating option would be the coating condition rating for the entire structure concerned. NCHRP Synthesis 25741 and ASHTO Guide for Painting Steel Structures42 are cited here as reference publications on Maintenance Painting. 4.2 Full Removal and Re-Coating 4.2.1 General If the area with poor condition rating (visible metal, corrosion, blistering, loose primer) and Rust Condition Category 4 is above 20% of the total surface area for primary components, then the structure requires total re-coating via contract in the future. If the area with Poor Condition rating is over 40% of the total area for secondary structural components (e.g. railings) then they require re-coating via contract in the future. The timing of the contract may depend on other rehabilitation needs, traffic management issues, section losses, accessibility and the future plans for the structure. 4.2.2 Full Removal by abrasive blast cleaning and recoating The standard practice of the ministry has been to abrasive blast clean to SSPC- SP 10/ NACE No. 2 Near White Metal standard, using a full enclosure with negative pressure in conformance with OPSS 91143, and recoat with a low VOC three coat paint coating system from the DSM list11. This method of full removal and recoating has given satisfactory service performance in the recent past. However, the environmental and

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occupational health and safety considerations, along with escalating costs associated with this practice has led to the development of alternative maintenance coating options in the United States and elsewhere. 4.2.3 Full Removal by High- and Ultrahigh-Pressure Water Jetting and

Recoating Another possible coating option would be to perform total removal of existing coatings by high/ultrahigh-pressure water jetting to SSPC-SP 12/NACE No. 544 Condition WJ-2, NV-2 as an alternative to dry abrasive blast cleaning to SSPC SP-10/ NACE No. 2 Near- White Metal standard9 and then use a 3 coat low VOC paint system that has been approved for coating over an abrasive blast cleaned surface. Since the use of high or ultrahigh- pressure water jetting does not produce a surface profile, this option is only possible for surfaces that have an existing surface profile of 25 –75 microns [i.e. previously abrasive blast cleaned (and coated) surfaces] unless a surface tolerant coating system is used. One of the advantages of cleaning by water jetting is that it removes invisible contaminants such as chlorides more effectively when compared with dry abrasive blast cleaning45. However, the access to difficult areas in a bridge may pose a bigger problem for cleaning by water jetting operations compared to dry abrasive blast cleaning, considering the sizes of the water-jetting wands/tools that are presently available. Another factor to be considered is the collection and disposal of wastewater generated during this operation. The use of high- and ultrahigh-pressure water jetting for surface preparation of steel for recoating is a relatively new technology, which has gained wide acceptance for cleaning of cargo ships, naval vessels and storage tanks. Performance data of this option for cleaning and coating of bridges are not available at the present time. However, one would expect the life expectancy for coatings applied over SSPC-SP 12/NACE No. 5, Condition WJ-2, NV-2, surface, to be about the same as that for the abrasive blast cleaned surface (to SSPC SP-10/NACE No. 2). This coating option is at a developmental stage; trial projects are being conducted to gather first hand experience in utilizing this new technology for bridge coating projects and to gather pertinent information concerning collection and disposal of wastewater generated during water jetting operations. 4.3 Zone Painting 4.3.1 General Zone painting is a viable option when deterioration of coatings is localised, (e.g. ends of girders under leaking expansion joints, lower portion of through trusses subjected to direct salt splashing). If the area of Poor Condition rating according to OSIM12 exceeds 10 % of the total surface area for a primary component, or is up to 20% for a secondary component, then that zone warrants cleaning, surface preparation and re-coating via contract. This may be undertaken either along with other rehabilitation work or by itself as a coating contract, depending on the total area to be coated. This may also depend on

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accessibility and possible options available for narrowing of the lanes or closing some lanes during rehabilitation work. With regard to the new weathering steel girders, the ministry policy is to paint the ends of girders at expansion joints up to 3 metres after blast cleaning to SSPC-SP10. This is an example of zone painting of new steel. 4.3.2 Options for Zone Painting Surface preparation and Coating system specifications for zone painting can be as follows: i) Blast cleaning to SSPC-SP109 and application of a low VOC three coats paint

coating system listed in the DSM11. (Option A). or ii) Power Tool cleaning either to SSPC-SP339 and/or SSPC-SP1140 and application

of an MTO approved coating systems for marginally prepared surfaces in conformance with OPSS 17045 and OPSS 91143(Option B).

or iii) Surface preparation by high pressure or ultra high pressure water-jetting to SSPC-

SP 12/ NACE No. 544 Condition WJ-2, NV-2, followed by blow drying with clean compressed air and application of an MTO approved coating systems for marginally prepared surfaces in conformance with OPSS 1704 and OPSS 911(Option C).

Estimated Service Life

Option A 20-25 years Option C 15-20 years Option B Cleaning Method

Power Tool Cleaning to SSPC SP-3: 6-10 years* Power Tool Cleaning to SSPC SP-11: 8-12 years*

[*For overcoating options, since the existing coating in sound/good condition is still intact (and overcoated with the new overcoating paint coating), the estimated service life given is the extension of service life beyond the remaining service life of the existing coating]. Site situation, the type of the existing coating and other factors related to costs and life expectancy of the coating system need to be considered when choosing the appropriate method for zone painting. The use of salt removal agents may be necessary especially for options B & C to reduce the amount of chlorides and other salts on the steel surface. In such situations wash water need to be fully contained conforming to the environmental regulations. As such, it is necessary to prepare a NSSP to incorporate surface preparation, coating application and the management of wash water and all other materials generated.

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4.4 Overcoating 4.4.1 General Overcoating is generally defined as the practice of painting over an existing coating as a means of extending its useful life35. Overcoating typically includes preparing the rusted spots or degraded areas by mechanical, chemical or water cleaning methods; feathering the edges of the existing coating to provide a smooth transition at the interface between existing sound paint and cleaned areas; spot priming with a surface tolerant coating, then power washing of the entire structure to remove loose chalk, dirt, dust, grime and other debris; applying full intermediate coat over the existing sound coating and repaired areas and, finally applying a full top coat over the entire structure (optional but recommended in most instances)46,47. The primary driving force for this approach in coating maintenance has been the cost of performing the work, especially in connection with a lead based paint. Since this procedure of overcoating inherently involves less coating removal and less extensive surface cleaning/preparation, which could be performed without extensive environmental protection, the cost is substantially less compared to total removal by abrasive blast cleaning and repainting. However, the service life of overcoating is, in general, much shorter compared to the coating applied over abrasive blast cleaned steel. A recently completed ministry study1 on “ Steel Bridge Coating Program – Cost and Option Study” makes the following conclusion and recommendation with regard to overcoating: “Overcoating is not a competitive option if it is not feasible as the initial treatment. However if there is a need to minimize the funding required over a period of time, or to spread funding onto more bridges, then overcoating could be applied to some bridges where conditions are suitable. For the 30 – 43% of the bridge inventory in which overcoating might be suitable as an immediate treatment, additional tests (DFT, adhesion etc.) have to be carried out to ascertain their suitability”. 4.4.2 Overcoating as a Maintenance Coating Option- Factors to be

considered a) General The decision on whether to use overcoating should take into consideration the long-term rehabilitation program for the bridge concerned. It should be borne in mind that overcoating is estimated to extend the service life of the existing coating by 8-12 years compared to the 20-25 years of life expectancy for full removal and re-coating. The ministry, at present, does not have any performance data of its own on overcoating projects. The information available in the literature amply reveals that for overcoating project to be successful, careful consideration should be given in the selection of candidate structures, in addition to the selection of suitable coating system and construction procedures.

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b) Condition of the Existing Coating The most important consideration is the condition of the existing coating itself. Although coating breakdown may be insignificant when first inspected, this deterioration is ongoing with a linear increase around the 0.1% - 0.3% surface rust mark12, thereafter the rate of deterioration increases more rapidly16. To consider overcoating as an option, the total amount of coating breakdown (rust) should be less than 3% (based on ASTM D610 and SSPC-VIS 2) at the time of maintenance painting. When the percentage of coating deterioration is higher, there is much higher risk of failure apart from higher cost associated with surface preparation/spot repair and application of coating (not economical). On the average, ministry construction projects require a two-year period for design, contract preparation and execution, after the initial inspection of the structure. Since coatings continue to deteriorate at an increasing rate over time, it is necessary to consider only the structures that have a much smaller percentage of coating failure at the time of inspection. In our assessment based on OSIM12, if the combined area of coating in Fair and Poor condition is 25 %- 50 % of the total area (with Poor condition is less than 10% of the area) of coating on the steel member, with the rest of the area in Good Condition, then a detailed coating condition survey is warranted if overcoating is to be considered. c) Type of Structure As stated previously, the ministry has about 725 steel structures of which 250 are weathering steel structures with the rest being carbon steel structures. Of the carbon steel structures, about 350 are girder type and the rest (about 125) are truss type structures1. The truss type structures are usually complex with numerous elements. Maintenance painting of truss structures is more labour intensive and the cost of access is usually much higher than for girder bridges. Furthermore, the coating condition rating for truss structures is done for the whole structure and not for the individual members. Such an overall rating introduces some uncertainty with regard to the extent of cleaning required for overcoating projects. Considering this uncertainty, along with the limited life expectancy for overcoating projects when compared to the full removal and recoating, one would prefer full removal and recoating for truss structures. (Abrasive blast cleaning of the steel structure to SSPC- SP10/NACE No. 2 and recoating with approved coating systems, which would last at least 20 years or more). However, there may still be situations where the engineer may consider overcoating as an option of maintenance painting for truss structures. This will be based on the condition of the coating and other considerations; in such cases, a project specific life cycle financial analysis should be carried out to assess the economics of the overcoating option. The carbon steel girder structures would be the prime candidates for overcoating projects. Between the years 1982-1998, 234 ministry bridges have been recoated1, which represents 38% of the carbon steel bridge inventory. It is reasonable to assume that the candidates for overcoating projects would most likely come from this list of bridges, which have been recoated after 1982. However, structures which have been coated prior to 1982, may also qualify if the criteria based on the condition of the existing coating are

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met. Clive Hare 48, one of the well-known specialists in this field, cautions, “Wherever possible, limit overcoating to bridges that were blast cleaned before the application of lead-based paint (or existing coating) i.e., bridges built after 1970". His recommendations with regard to avoiding overcoating failures are given in the next section. 4.4.3 Risks Associated with the Overcoating Process The main risks associated with overcoating are35, 48,49

a) Delamination b) Premature failure due to recurring corrosion and deterioration at spot

cleaned areas Factors that affect the above mentioned risks in overcoating are as follows35: i) Condition of the exiting coating including thickness and adhesion. ii) Condition of the steel substrate, corrosion pattern and extent. ii) Surface contaminants such as soluble salts, oil, dirt, debris including bird droppings. iv) Coating compatibility v) Type of structure vi) Exposure environment 4.4.3.1 Delamination A primary risk associated with overcoating is that the overcoating system may cause delamination of the existing coating system. Delamination is primarily due to the internal stresses in the overcoat material being transferred to existing coating layers. Internal stress in a coating layer is mainly due to shrinkage of the coating material or system during drying/curing and aging and is dependent on the chemical composition of the coating material and the curing mechanisms involved. Many of the overcoating systems, therefore, have been formulated as high solids systems with low shrinkage stress. The other factors that affect the internal stress include coating thickness, film-forming conditions, coating age, temperature and temperature fluctuations. Low internal stress on the existing coating is vital if the overcoating project is to succeed. The reduction in internal stress can be addressed at the formulation and/or overcoating system design stages48. With regard to the formulation, many approaches have been taken by the manufacturers to mitigate internal stress (that is incurred in overcoating projects). The major emphasis has been in resin design. Here, the emphasis should be to reduce cross-link density and the glass transition temperature (Tg )48. The result is a flexible system that incurs less internal stress during curing and more readily allows strain relaxation. A greater molecular distance between reactive groups on the curing agent yields a final film that is more flexible and stress dissipative. Highly reactive or functional cross-linking agents are not wanted because they increase the brittleness of the film. Flexibilizers, such as the aromatic hydrocarbon resins, plasticizers, and reactive chain stoppers, have been used in

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formulations to reduce curing rates. This results in improved adhesion as well. The use of aluminum and other platey pigments are beneficial because they tend to dissipate stress. Other beneficial effects on reducing internal stress, in the case of aluminum pigments, come from the fact that these pigments effectively reflect UV light and heat, thereby reduce the rate of oxidative changes to the film. In addition, better barrier properties of platey pigments play a role in mitigating stress build up resulting from moisture penetration into the film48. With regard to the system design, Clive Hare48 suggests the following:

- Wherever possible, limit overcoating to bridges that were blast cleaned before the application of the existing coating (or lead-based paint- i.e., bridges built after 1970).

- Prepare the bare steel areas as well as possible, preferably with scarifying tools. - Apply spot primers in 2 or more coats to a film thickness of 10 mils (250 µm)

total, but only over the corroded areas. - Minimize the number of coats applied to areas of the substrate still bearing intact

existing (or lead-based) paint. - Note that the overcoating will be less likely to succeed where the system is

subject to severe fluctuations in temperature and humidity (especially sharp falls in temperature).

- Do not use the overcoating approach where there is clear evidence of existing

widespread adhesive or cohesive deficiencies in the existing coating system. a. Effect of Dry Film Thickness (DFT) The risk of delamination is higher when the DFT of the existing coating is either too low or too high. Based on the Alberta Transportation and Utilities Guidelines24, it is recommended that the dry film thickness (DFT) values of the existing coating should be between the range of 75 µm and 350 µm (3 mils - 14 mils) for considering overcoating as an option for MTO structures. b. Coating Compatibility For the overcoating process to be successful, it is necessary that the overcoating system to be used is compatible with the existing coating in the structure and that the new coating material adheres well to the existing coating and the steel substrate where exposed. If the overall compatibility is poor, failure due to cracking, delamination, and peeling will occur. Here the term compatibility encompasses material compatibility between the two different coating systems (or chemical compatibility) as well as the ability to retain the integrity of the whole composite system without the above mentioned

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failures, during application and curing/drying of the overcoating system and service conditions. The coating compatibility could be assessed in the field by conducting a Patch test; in accordance with ASTM D 506437.This is a practical field method for assessing the overall suitability of the existing coating to accept an overcoating system or systems under evaluation. c. Adhesion An important factor to be considered in assessing the risk of delamination is the adhesion of the existing coating system. A loss of adhesion of the existing coating system at either the steel/coating interface or within the layers of the existing coating may result in delamination and failure of the overcoat. The existing coating needs to be somewhat flexible to achieve good adhesion with the overcoating system. Heavily aged brittle coatings are not suitable substrates for overcoating. Adhesion between the overcoat system and the existing paint is also affected by the presence of surface contaminants. Rust on the surface of steel in the deteriorated areas is a foreign material and will effectively prevent chemical adhesion because it separates the coating and the substrate. Loose rust is particularly problematic, for the coating has to wet and bind the rust into its continuum during application and drying. 4.4.3.2 Premature Failure Due to Recurring Corrosion and Deterioration Another risk associated with overcoating is that the original/existing coating along with overcoat system may not provide an adequate period of service primarily due to the ongoing degradation of the coating material and recurring corrosion of the steel surface due to severe service environment. This type of degradation may be manifested by pin- point rust, undercutting at small breaks in the coating system or blistering. Low DFT of the existing coating, presence of rust and surface contaminants affects the performance of the overcoating. The extent and the type of surface preparation used prior to overcoating significantly affect the performance of the overcoat systems. For example, power tool cleaning to SSPC-SP 3 would not remove the rust fully and these areas are more prone to corrosion and rusting if oxygen and moisture could get in. Furthermore, many overcoating systems are formulated to be tolerant barrier systems without the galvanic benefit of zinc; these systems are less tolerant to the level of chloride contamination. 4.4.4 Overcoating Materials The paint system for overcoating shall be one of the MTO approved systems for marginally prepared surfaces.

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4.5 Touch-Up 4.5.1 General Touch-up refers to spot cleaning by power or hand tools and painting the affected areas only, as compared to overcoating which requires spot priming, followed by application of mid coat and top coat over the entire or designated area of the structure. It is economically advantageous to touch-up coatings before serious coating deterioration or corrosion occurs. It is therefore recommended that the touch-up of the bridge coatings be undertaken, where feasible, before the deterioration reaches 3% rust mark (i.e. when the coating in general is in Fair condition, with the deterioration/rust mark in the range of 1-3%). It is essential that every effort be made to try to avoid large rusted areas that require expensive surface preparation operations (e.g. blast cleaning). The coating life is, to a large degree, determined by the cleanliness of the steel surface to which it is applied. A coating applied to a rusty substrate or on a flaking paint will not last as long as the one applied to a blast-cleaned surface. Bearing this in mind, the following situations may be repaired as follows: 4.5.2 Touching-up Intact Coatings An intact coating free of defects such as blisters should be left in place. After thoroughly washing the surface to remove contaminants, extra coatings may be applied. Existing coating may have to be abraded in order to topcoat them. This surface roughening may be done by power tools/discs on small areas or power tools with vacuum attachment on larger areas. 4.5.3 Touching-up Slightly Flaked or Blistered Coatings Where the coating is reasonably adhered to the steel with a slight degree of flaking or blistering but no surface rusting, remove the loose paint by any means practical. A good power wash of the steel surface at a water pressure of about 10 MPa should be carried out before new coats are applied. 4.5.4 Touching-up Rusted Areas If there is coating failure with substrate corrosion, then the deteriorated coating and rust shall be removed. These areas should be repaired as follows: i) Remove all visible oil and grease by SSPC-SP 1Solvent Cleaning38, from areas

that are to be coated. ii) Remove all loose rust and loose paint to the requirements of SSPC-SP2 (Hand

Tool Cleaning). However cleaning to SSPC-SP3 -Power Tool Cleaning39 standard or SSPC-SP7 Brush-off Blast Cleaning50 standard (especially a vacuum shrouded

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equipment) would be preferable. Feather the edges of the intact coating so that about 2 mm - 4 mm of all coats are exposed.

iii) If the original topcoat is grey, (it could be alkyd, epoxy mastic, vinyl paint,

polyurethane or acrylic), apply epoxy-mastic to a total dry film thickness of 225 µm in the bare spots. If the original topcoat is green, (indicating alkyd paint), apply a single coat surface tolerant paint system which is quite flexible after curing (e.g. calcium sulfonate based system- Termarust 210051) to a total DFT of about 250µm in matching colour.

4.6 Guide for Selection of Maintenance Painting Procedure

A general guide for the selection of suitable maintenance painting procedure, based on coating condition rating and bridge maintenance and rehabilitation schedules, is presented in Table 4.1.

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Table 4.1

Maintenance Coating Guide Based on Coating Condition Rating and Localities of Coating Deterioration

Coating Condition rating Fair Condition

Poor condition

Feasible Treatments Comments

>50% < 10% Scattered throughout

Overcoating of the entire structure after SSPC-SP 3 and localized SSPC-SP 11 Surface Preparation

SSPC-SP 11 cleaning of corroded patches larger than 100 cm2. Vacuum shrouded power tool would be the preferred option for SSPC-SP 11 cleaning.

>50% < 10% localised

Overcoating of the entire structure with Zone painting of localized poor areas after SSPC-SP 11 Surface preparation

Vacuum shrouded power tool would be the preferred option for SSPC-SP 11 cleaning

60% - 90% 10% - 40% localized

Zone painting of localized poor areas after SSPC SP 10 or SSPC-SP 12 Surface preparation and Recoating of fair areas (Optional)

Full enclosure with negative pressure is necessary for SSPC-SP 10 cleaning. A collection (and filtration) system is required to collect the processed water during SSPC-SP 12 surface Preparation

60% - 80% 20% - 40% Scattered throughout and not localized

Total Removal by* SSPC-SP 10 and recoating with a 3 coat paint system for abrasive blast cleaned surface from the DSM or Total removal by SSPC-SP 12 and recoating with a coating system for marginally prepared surfaces from the approved systems.

Full enclosure with negative pressure is necessary for SSPC-SP 10 cleaning. A collection (and filtration) system is required to collect the processed water during SSPC-SP 12 surface Preparation

0ver 40% Same as above Same as above

*Abrasive blast cleaning to SSPC-SP5/NACE No. 1 and metallizing & sealing, or hot dipped galvanizing may be considered on a case–by-case basis.

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5. PLANNING 5.1 General All factors that may affect the coating contract must be investigated before the contract package is assembled. The offices charged with responsibility for the environment, vehicular traffic control, navigable water, etc. must be contacted so their requirements can be incorporated into the contract. Structural steel coating should be carried out under a separate contract52 (See Appendix I). Where it is included as part of a bridge rehabilitation project, it may, as in the past, result in unrealistic underbidding of the coating item; the use of unqualified local contractors unversed in bridge work leading to poor quality or work carry-over; and the relegation of the coating item to the latter stages of the contract schedule resulting in unfavourable weather conditions. If a coating contract is combined with a structure rehabilitation contract, it should only be done after careful analysis shows there are savings to be gained by sharing access facilities, traffic control equipment and/or environmental protection devices. If it is deemed economical to proceed with a combined contract, the rehabilitation work must be completed prior to the coating work. This will avoid damage to the freshly coated steel. Where damage will not occur and where later access may be difficult, then carry out the coating work before the rehabilitation of the structure. Contract preparation is the responsibility of the Regional Structural Section’s Project Manager. 5.2 Review of Data The Project Manager must be familiar with the following:

• existing structure drawings; • maintenance inspection file; • site conditions (topography and traffic volumes); • district concerns; • future plans for the bridge; • other proposed contracts in the vicinity (Ministry or Municipality); • Recent literature on coating materials (References 1, 5,7, 47, 48) and DSM

listing (Reference 11); • OPSS 911 – “Construction Specification For Coating Structural Steel

Systems” (Ref. 43); • Ontario Structure Inspection Manual (Ref. 12); • Structural Steel Coating Manual (Year 2003 Edition); • Ontario Traffic Manual Book 7 – Temporary Conditions53, 2001, Queen

Printers of Ontario. The more important items of information from the above are discussed below.

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5.2.1 Existing Structure Drawings

• structure type and size; • unusual design features (inaccessible areas, truss boxes, etc.); • roadway width (for staging); • any attachments to the structural steel (utilities or railway baffle plates); • expansion joints – locations, type; • deck drains and pipes.

5.2.2 Maintenance Inspection File

• history of deterioration; • areas where coating failure occurs most frequently; • previous cleaning/surface preparation methods employed; • types of previous coatings, presence of lead and chromium pigments.

5.2.3 Site Conditions Visits made to the site, as discussed in Section 2.2, can be useful in establishing:

• traffic conditions; • geometry of adjacent highway; • options for staging (including detours); • inaccessible areas; • nature and extent of deterioration; • deviations from design information; • any unusual features (e.g. utilities, etc.); • need for liaison with other authorities; • any utility attachments or appurtenances not shown on the as-built drawings. • if overcoating is intended, whether the coating condition is still within

applicable limits. 5.2.4 District Concerns District Maintenance staff should be contacted to see if they have any concerns that may bear on any final decisions.

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5.3 Environmental Protection An environmental protection item is to be included in each contract involving coating of existing structural steel, unless otherwise determined by the Regional Environmental Unit. The type of enclosure under environmental protection item would depend on the surface preparation method to be specified as well as on the type and method of application of coating material. Total removal of existing coatings by abrasive blast cleaning would require a full enclosure with negative pressure, whereas power tool cleaning would require only a partial enclosure. A partial enclosure is also adequate during brush or roller application of coating materials, but a full enclosure is required during spray application of paint coatings. OPSS 911 and Special Provision 911 S01 “Environmental Protection During Coating of Existing Structural Steel and Railing System” will constitute the prime requirements for this item. It is to be noted that a memorandum of understanding between MTO/MOE54 is in place. Before a project is specified to be conducted entirely or in part as night work, the Regional Environmental Unit will make application, on behalf of the Contractor, to the affected municipal council(s) for exemption from any night-time noise bylaw constraints. Formal exemption ensures that the Contractor (otherwise bound by municipal by-laws) will be permitted to conduct nighttime operations. The details of the exemptions are to be outlined in the contract. Special Provision 911 S05 “Management of Spent Blasting Medium and Disposal of Removed Coating Material and Spent Blasting Medium” is to be included in all contracts, (which require surface preparation by abrasive blast cleaning). It is to be noted that spills response requirements are as per MTO General Conditions. The Regional Structural Section will provide the Regional Environmental Unit with sufficient notice of upcoming contracts involving coating of structural steel so that site investigations can be conducted under summer conditions prior to contract preparation. Where environmental protection measures to be incorporated in Structural Steel Coating Contracts are at variance with these guidelines, they will be reviewed by the Regional Environmental Unit with the Environmental Policy and Standards Section (Provincial & Environmental Planning Office). The Regional Structural Sections will assemble the protection measures in the contract package as recommended by the Regional Environmental Unit. This will be done after any review and consultation between the Regional Environmental Unit and the Environmental Policy and Standards Section.

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5.4 Traffic Control and Protection The method of traffic control and protection of construction personnel must be decided from the following options or combinations, as detailed in the Ontario Traffic Manual, Book 7, Temporary Conditions53. Traffic Control: • road closure

• lane closures • detours • temporary signals • traffic control persons • remote control flaggers • night work • cones • construction markers

Traffic Protection: • flexible drum or barricades

• temporary New Jersey barriers • temporary steel beam guide rail • temporary steel beam attached to existing posts

Where a convenient detour exists or can be constructed, it is often advantageous to close a road to traffic during coating operations. This allows the contractor to operate with maximum efficiency and, consequently, is the most economical solution. The time that traffic is disrupted shall be kept to a minimum. Where closures are being considered, it is essential that emergency services and local authorities be advised early in the planning stage. However, the opportunity to detour traffic is rarely available and most coating contracts are carried out in stages. Traffic control shall provide safe passage through the construction zone while keeping the disruption of traffic flow to a minimum. The number of lanes required, lane widths, and the need for speed restrictions will be determined by the Regional Traffic Section. Temporary lane widths will not normally be less than 3 m. The traffic control plan for construction staging and lane closures will be determined jointly by the Planning and Design, Traffic, Structural and Construction Sections in the Region. It is essential that the traffic control plan be finalized before detailed design work begins. The Planning and Design and Traffic Sections shall decide whether signing, traffic control persons or temporary signals are required at the site. Traffic control devices include construction markers, temporary New Jersey barriers, or temporary steel beam guide rail. Any non-standard control devices should be covered in the special provisions. In all cases, traffic control measures must conform to the requirements of the Ontario Traffic Manual, Book 7, Temporary Conditions53.

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Night work on high traffic volume roads can also be used to mitigate traffic delays. Two aspects of night work that must be carefully monitored are lighting and weather conditions. Proper lighting is vital, not only for the blasters and painters, but also for the Ministry’s inspectors to check the work for conformance to specification. A separate tender item should be used in the contract, and a special provision entitled “Site Illumination” has been written (see Part 2 of the Manual) which specifies a minimum lighting value of 400 lux at any point in the work area for each phase of the construction and inspection. This SP should be included in the package when night work is deemed necessary. Problems may occur during night work relative to application temperatures and dew point. The Society for Protective Coatings specification, SSPC-PA155, specifies that the steel surface temperature must be a minimum of 3oC above the dew point before painting is allowed. This criterion is mandatory and should be achievable between May – August in Southern Ontario; and June – July in the rest of the Province. Two other aspects which should be investigated if night work is contemplated are: an exemption from the noise by-laws of local municipalities may be needed; and provisions for parking the contractor’s equipment on or off the right-of-way during daylight hours. The contractor’s equipment shall not be placed where it may pose a safety hazard or impede the flow of traffic. Once the traffic control plan has been formulated, the Project Manager should inform all interested parties, including emergency services and the media.

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6. DESIGN 6.1 General 6.1.1 Mechanism of Corrosion and its Control by Protective Coatings Corrosion is the deterioration of a material, usually a metal, because of a reaction with its environment. It is an electrochemical reaction (sometimes called galvanic action). The following four essential elements must be present for corrosion to occur18, 19.

• An anode (that corrodes) • A cathode (that does not corrode) • An electrolyte external path • A metallic pathway to complete the circuit

Protective coatings and other systems that interfere with one or more of these components can be used to control corrosion. Protective coatings on structural steel interfere by three basic mechanisms:

• Barrier Protection- Most coating films form a barrier to isolate the metal surface from electrolytes in the environment. e.g. epoxy zinc/epoxy/polyurethane, or epoxy zinc/water-based acrylic/water-based acrylic, or epoxymastic system;

• Chemical inhibition- Chemical components added to the coating may inhibit anodic or cathodic reactions. e.g. chromates, molybdates, borates, zinc phosphate, red lead, calcium sulfonates;

• Galvanic (Cathodic) protection-The use of a primer heavily loaded with zinc particles, galvanizing and metallizing provide galvanic protection to the base metal (steel). These coatings also provide barrier protection to varying extents.

6.1.2 Structural Steel Coatings, Bridge Environment and Coatings

Durability Structural steel coatings must perform in every type of macro environment, from the mild rural atmosphere to the severe industrially polluted atmosphere. Structural steel coatings in bridges and other highway structures in Ontario are subjected to exposure to de-icing salts, to wetting and drying, to freezing temperatures, to blistering sunlight, and to all types of atmospheric pollutants including acid rain. It is not surprising that coatings break down, if not from the above, then inevitably from degradation due to the aging of the coating itself. When coating breaks down (in the case of barrier protection) or when the galvanic coating is consumed, corrosion of steel sets in. In addition, contaminants trapped underneath the coating at the steel surface have pronounced effect on corrosion of the steel substrate and the coating breakdown.

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6.2 Coating Policies and Practices of the Ministry Between 1986-1996 In 1985, the Ministry adopted the following policy: Effective 1986, all coating contracts would specify the removal of all existing coatings and rust (See Appendix II), with one of the following cleaning/surface preparation requirements: • Joint Surface Preparation Standard SSPC-SP6/NACE No. 3- Commercial Blast

Cleaning; • Joint Surface Preparation Standard SSPC-SP10/NACE No. 2 - Near-White Blast

Cleaning; • Joint Surface Preparation Standard SSPC-SP5/NACE No. 1- White Metal Blast

Cleaning; or • Surface preparation Specification No. 8 Pickling - SSPC-SP8 (1982). In 1985, the Ministry had also decided to curtail the use of zinc chromate/alkyd based coating system (See Appendix III), based on the many examples of premature coating failure on contracts that had used this coating system. Alkyd coatings have poor resistance to a road salt environment, resulting in a life span much less than anticipated. The coating systems that were used during this period included inorganic zinc/vinyl/vinyl and epoxy zinc/vinyl/vinyl system on SSPC- SP 10/NACE No.2 blast cleaned surface and coal tar epoxy system on SSPC-SP 6/NACE No. 3 blast cleaned surface. Aluminium filled epoxy mastic system was also used to a smaller extent on SSPC-SP 6/ NACE No. 3 blast cleaned surface until 1988. The above mentioned coating systems contained more than 350 mg/l of volatile organic compounds (VOC) and, as such, are classified as high VOC coating systems. Galvanizing and thermal metal spraying (metallizing) were used for coating handrails, other railing systems and highway appurtenances. Hot-Dipped galvanizing had also been used for coating five steel girder bridges between 1991 and 19961. Hot-dipped galvanizing requires the steel surface to be cleaned to an SSPC-SP 8 Pickling standard, while metallizing requires the steel surface to be abrasive blast cleaned to SSPC-SP 5/ NACE No. 1 White Metal Blast standard10. 6.3 Current Coating Policies and Practices of the Ministry (Since 1996) 6.3.1 Paint Coating Systems In 1996, the Ministry decided to terminate the use of high VOC coating systems and embarked on the use of low VOC coating systems. This decision was mainly based on environmental considerations without compromising on the service performance expected. As in the past, it was necessary that the coatings to be used in ministry contracts be selected from the pre-approved list of products in the ministry’s designated sources materials (DSM) list. Pre-approval was based on laboratory evaluation conforming to the OPSS 1704 Material Specification5 for Structural Steel coatings. Since 1996, in almost all the bridge coating contracts, low VOC paint coating systems have been used for maintenance painting, after full removal of the existing coating.

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The Low VOC Paint Coating Systems in the current approved list are as follows11:

Coat System 1 System 2 System 3 System 4 Primer Epoxy Zinc Epoxy Zinc Inorganic Zinc Inorganic

Zinc Mid coat Water-based Acrylic Epoxy Water-based Acrylic Epoxy Topcoat Water-based Acrylic Polyurethane Water-based Acrylic Polyurethane

6.3.2 Surface Preparation Requirements for Low VOC Coating Systems The surface preparation required for the above low VOC three coat paint coating systems is abrasive blast cleaning to SSPC SP-10/NACE No. 2 Near-White Metal standard9 having a surface profile within a range of 25 –75 microns43. 6.3.3 Metallic Coatings (Hot-Dipped Galvanizing and Metallizing) Hot-dipped galvanizing and metallizing (metallic coatings) could be the two other options if total removal is considered. Hot-dipped galvanizing is essentially a shop operation, while metallizing could either be performed at site or offsite in a shop. Although these two recoating options were available, these methods were seldom used for coating bridges in the past, mainly due to the high initial costs. However, advances in metallizing technology and the availability of larger galvanizing kettles for hot-dipped galvanizing have made these processes more cost competitive in terms of life cycle costs (LCC). As stated previously, hot-dipped galvanizing was employed for recoating of five steel girder bridges between 1991 and 19961. Metallizing was performed in the shop for recoating of a ministry bridge in 19987. (See Section 1.3 for surface preparation requirements). 6.3.4 Total Removal – Its Advantages and Implications Total removal of all existing coating is advantageous for the following reasons: the majority of the old coatings constituted of lead or chromate based paints and they are designated hazardous substances which need to be properly disposed; total removal of the existing coating would eliminate the hazardous materials once and for all; cleaning of the steel to near-white metal condition provides the new coating systems a better/clean substrate for a longer service life; and because longer service life is achieved, the mobilisation and traffic protection and user costs are kept to a minimum over the life of the bridge. The service life of the coating achievable by this approach is 20 years or more.

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6.3.5 Environmental Protection Requirement Since 1994, it has been the Ministry’s standard practice to require a full enclosure with a negative pressure whenever total removal of the existing coating and abrasive blast cleaning is carried out. 6.3.6 Cost Implications and Other Coating Options Coating cost for bridges has escalated significantly during the last decade mainly due to the cost associated with environmental protection for full removal by abrasive blast cleaning. This is not unique to Ontario. Escalation of costs, sometimes coupled with dwindling funding for bridge coating projects, has prompted many US agencies41 and some Canadian provinces including Ontario to incorporate overcoating as an option of maintenance painting of bridges. Ministry has already approved some coating systems (surface tolerant coating systems) for this application. As stated in a previous chapter, protective coatings of a bridge are subjected to many different microenvironments ranging from benign to highly corrosive areas such as under the leaking expansion joints. This often results in corrosion in localised areas due to the breakdown of coating in these areas, while the coatings in the rest of the areas of the structure remain in sound (excellent to good) condition. Cost consideration also has resulted in such situations to adopt zone painting of the affected areas. 6.4 New Steel Since 1968, the Ministry has used C.S.A. G40.21 Grade 350 A weathering steel or Atmospheric Corrosion Resistant (ACR) steel exclusively for new construction 3. Current policy calls for the following: a) Structures with Expansion Joints: All weathering steel, including diaphragms and inside surface of box girders, but excluding surfaces in contact with concrete and the contact surfaces of bolted joints to be cleaned to the requirements of SSPC-SP 10/NACE No. 2 Near-White Metal standard and shop coated with epoxy zinc/epoxy/polyurethane coating system for a distance of 3 metres from the end of the girders, (wherever there is an expansion joint or as specified in the contract documents). b) Structures with Integral Abutment: Exterior surfaces of ends of weathering steel girders at integral abutment to be cleaned to the requirements of SSPC-SP 10/NACE No. 2 Near-White Metal standard and shop coated in accordance with Structural Manual56 to a distance of 600 mm in total from the face of the abutment towards the centre of the bridge and a total of 100 mm towards the end of the bridge, which is based on the recommendations given in Report BO-99-04 57.

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The coating should be applied in three coats, as specified in OPSS 91143, with the first coat (primer) 75 µm minimum thickness, the second coat 100 µm minimum thickness and the third coat 50µm minimum thickness. Topcoat of the coating system shall be a semi-gloss equivalent of 20045 brown of the US Federal Standard 595B Colors (as specified in the OPSS 17045) to match the colour of the patina on the rest of the steelwork. 6.5 Coating of Railing Systems The steel railing system attached to concrete or steel structures should first be checked whether the railing system meets the current standard. A substandard railing should be replaced with a new railing conforming to the current standards at the time when the deck is being rehabilitated. The steel railing system attached to concrete or steel structures that meets the current standard should be recoated when the combined area of rust and unsound paint exceeds 20% of the steel surface area. The railings should be removed and hot dipped galvanized, where feasible. If galvanizing is not practical, or removal of the rails is not possible, then the low VOC Paint Coating System 2 should be specified (See Appendix IV). Normally, the railing system is coated when the rest of the bridge is coated. If any part of the steel railings is damaged (e.g. bent balusters), or if the components of the rails are connected with incomplete welds, then these defects should be repaired prior to galvanizing. When the rails are to be galvanized and where it is not feasible to remove the steel posts, the posts should be metallized using either pure zinc or using Zn/Al 85/15 alloy metallizing wire, after abrasive blast cleaning to SSPC-SP 5/NACE No. 1. If metallizing is not a viable alternative, then the posts should be coated with Epoxy Zinc/ Epoxy/ Polyurethane (System 2), after the required SSPC SP-10/NACE No. 2 surface preparation. Where the rails are removed, temporary traffic protection must be used according to the requirements given in the section on “Traffic Control and Protection”. 6.6 Localized Coating Failure If regular inspections, in conjunction with past history, reveal a pattern of localized coating failure (e.g. under expansion joints) it may be economically prudent to just address those areas. This could be done based on the guidelines provided in Section 2 of this manual for zone painting, overcoating and touch-up. Although thick coatings usually protect steel better than thin coatings, a point is eventually reached where internal stresses from the number of coats applied over the years, leads to cracking and flaking. It is not optimum to keep applying the same amount of paint to sound and rusted areas alike.

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If coating failure is occurring repeatedly around expansion joints, a contract should be set for zone painting, specifying total removal of the coating and rust at the affected area and at least one metre beyond the area of deterioration. Then the new coating should be applied to the thickness shown in Table 6.2. If the coating breakdown/rust on the remainder of the structure is below the 3% mark, no corrective procedures are necessary by contract, but it may be repaired. Before the coating is repaired, the leaky joint should preferably be replaced. 6.7 Field Identification of Existing Coatings The existing coatings must be identified in the contract package. If in doubt, samples should be taken (note where they are taken from) and after careful packaging, sent to the Materials Engineering and Research Office (MERO), Concrete Section in Downsview for analysis. Some information has already been provided in Section 1 of this manual. The following points will also help to identify the existing coatings: • To ascertain the primer, remove a portion of the topcoat. The old Alkyd system used

red lead primer, while the High Build Alkyd (See Section 1), used from 1974 – 1985, employed a yellow zinc chromate primer.

• The intermediate coat on the old Alkyd system consists of a grey Alkyd paint. • The top or final coat of the old system (prior to 1974) consists of a grey or green

Alkyd paint or Aluminum paint. • Aluminum paint is identified by scraping the top layer, exposing a silvery coating. • A galvanized coating (e.g. on a handrail) is smooth to the touch, while a metallized

finish feels like sandpaper. • The vinyl systems have been used since 1982 until 1996. • The epoxy mastic/epoxy mastic system has been used starting in 1986 – 1988. • Low VOC inorganic zinc/epoxy/polyurethane has only been used staring in 1995. • Low VOC organic zinc/epoxy/polyurethane has only been used starting in 1995. • Low VOC organic zinc/water-based acrylic/water-based acrylic has only been used

on some of the weathering steel girders and diaphragms of Willow Creek bridge. • Low VOC inorganic zinc/water-based acrylic/water-based acrylic has only been used

on some of the carbon steel girders and diaphragms of Willow Creek Bridge in 1995. • The colour of the finish coat for the low VOC system5 for carbon steel structure is a

semi gloss equivalent of either 501-101 grey (1-GP-12C) or 26307 grey (US Fed

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Standard 595B Colors). For Atmospheric Corrosion Resistant steel, the colour of the finish coat is a semi-gloss equivalent of either 504-217 brown (1-GP-12C) or 20045 brown (US Fed Standard 595B Colors).

6.8 Surface Preparation and Cleaning Requirements for the Approved

Coating Systems The surface preparation requirements for the low VOC paint coating systems in the DSM list11 are shown in Table 6.1. Table 6.1 also lists the surface preparation requirements for spray metallizing and hot-dipped galvanizing that could be considered for coating some bridge structures. (OPSS 91143, Subsection 3). Some of the generic requirements for the surface preparation of steel components include the following:

• Solvent cleaning to SSPC-SP 138 prior to blast cleaning and hand or power tool cleaning is pre-requisite, when visible oil, grease, soil and other soluble contaminants are on the steel surface. Blast cleaning usually does not remove these contaminants.

• The baked-on carbon residue from diesel trains is very difficult to remove by solvent cleaning. Abrasive blasting has, in the past, proven the only effective way of removing it.

• For faying surfaces, either an epoxy zinc primer or inorganic zinc primer from the low VOC coat systems should be applied to obtain frictional resistance values conforming to the CHBDC CAN/CSA S6-00 Canadian Highway Bridge Design Code 43, 58; the mid and topcoat should not be applied. Faying surfaces could also be metallized or galvanized.

• All the paint coating systems, including the seal coat for thermal spray metal coating and paint systems to be applied over galvanised coating, should be selected only from the pre-approved products lists.

April 2004 1-47

Table 6.1 – Coating Systems and Surface Preparation Requirements

Surface Preparation Requirement

COATING SYSTEM

SSPC-SP10/ NACE No. 2

Sept 2000 Near-White

Blast Cleaning

SSPC-SP11-87 Edit changes

Sept 2000 Power Tool

Cleaning

SSPC-SP3-82 Edit changes

Sept 2000 Power Tool

Cleaning

SSPC-SP12/ NACE No. 5

20027

SSPC-SP8-82 Edit changes

Sept 2000 Pickling

SSPC-SP5/ NACE No. 1

Sept 2000 White Metal

Blast Cleaning

Low VOC Epoxy Zinc/Water-Based Acrylic/ Water-Based Acrylic X X¹ X2

Low VOC Epoxy Zinc/Epoxy/Polyurethane X X1 X2 Low VOC Inorganic Zinc3/Water-Based Acrylic/Water-Based Acrylic X -

Low VOC Inorganic Zinc3/Epoxy/Polyurethane X -

Zinc/ Al Metallizing with a low VOC seal coat - X

Hot Dip Galvanizing alone or with a low VOC paint coating system4 (Duplex system) - X

Coal Tar Epoxy X5 - Low VOC coating systems for marginally prepared surfaces6 (surface tolerant systems) X X X

1. When the area to be cleaned and coated is small, SSPC-SP11 Power Tool Cleaning to Bare Metal could be specified. 2. This paint system could be used in place of a paint system for marginally prepared surfaces, provided the surface has a minimum profile of 25µm (e.g. surfaces

which have been previously abrasive blast cleaned). 3. Inorganic zinc primer is less surface tolerant compared to epoxy zinc primer. It requires a very clean surface (SSPC–SP 10/NACE No. 2 Blast Cleaning to

Near-Whiter Metal standard or better) for optimum performance. 4. Sign support columns receive paint coatings over galvanizing (Duplex system) to provide additional corrosion protection. Prior to paint coating application,

galvanized zinc coating needs to be brush blast cleaned using low hardness (Moh’s hardness of 6 & lower) to provide a clean surface for paint application. Abrasive blasting to SP6 may be required prior to pickling to remove existing coating.

5. SSPC-SP6/NACE No. 3 Commercial Blast cleaning standard is acceptable for coal tar epoxy system. 6. These systems are recommended for Overcoating projects. When overcoating is to be performed, surface preparation shall be performed to SSPC-SP 3 Power

Tool Cleaning standard throughout, except in corroded areas/rust patches which are greater than 100 cm2 in area, which require Power Tool Cleaning to Bare Metal –SSPC-SP 11/NACE No. 2 standard, prior to the application of an approved coating system for marginally prepared surfaces. Non-visible contaminants such as the chlorides need to be removed by the use of chloride removal agents during power washing. It is recommended that the designer contact the Bridge Office, MTO with regard to the preparation of a non-standard special provision for coating of existing structural steel and environmental protection.

7. Joint Surface Preparation Standard SSPC-SP 12/NACE No. 5 “ Surface Preparation and Cleaning of Steel and Other Hard Materials by High and Ultrahigh-Pressure Water Jetting Prior to Coating.

April 2004 1-48

6.9 Selection of the Coating System The selection of the coating system is a very important step in the preparation of a bridge-coating contract. Many factors must be considered, such as: • The location of the structure; • The structure’s importance in the highway system; • The volume of traffic at the site; • The impact of lane closures on traffic flow; • The type of structure (e.g. truss or girder); • The anticipated remaining service life of the structure; • Environmental considerations; • Application temperature requirements; and • The cost per m2/year of the proposed coating system. Selection of the most durable coating system is warranted for structures where lane closures may cause serious disruption to the normal flow of traffic. Coating systems with greater life spans reduce the frequency of re-coating and resulting traffic disruptions. 6.9.1 System Selection Criteria Table 6.2 provides pertinent information concerning the various (ministry approved) coating systems that could be considered for coating projects. The information provided includes factors such as the optimum utilization, surface preparation requirements, possible practical limitations in achieving the required surface preparation standards and the sensitivity of the coating systems to such situations.

April 2004 1-49

Table 6.2 – Coating System Selection- Factors to be considered Coating System (Total Minimum Dry Film Thickness)

Optimum Utilization Remarks

System 1 Low VOC Epoxy Zinc/Water-Based Acrylic/Water-Based Acrylic (75 µ m /75 µ m /75 µ m)

Has not been used since 1995; awaiting further evaluation/assessment on its service performance

Moratorium on its use is in place since 1997. Once the moratorium is lifted, it could be considered as an alternative to System 2 when multi-component, complex steelwork (e.g. truss) is to be coated.

System 2 Low VOC Epoxy Zinc/Epoxy/Polyurethane (75 µ m /75 µ m /75 µ m)

Suitable for all structure types

This system is more tolerant to the degree of surface preparation compared with System 4. Hence, it should be used for multi component, complex steel work (e.g. trusses). Service-life expectancy: 20 years

System 3 Low VOC Inorganic Zinc/Water-Based Acrylic/Water-Based Acrylic (75 µ m /75 µ m /75 µ m)

Has not been used since 1995; awaiting further evaluation/assessment on its service performance

Moratorium on its use is in place since 1997. Once the moratorium is lifted, it could be considered as an alternative to System 4

System 4 Low VOC Inorganic Zinc/Epoxy/Polyurethane (75 µ m /75 µ m /75 µ m)

Suitable for girder type structures.

Require very clean surface prepared to the SSPC-SP10 standard or better for its optimum performance. However, it is not suitable for truss type structures, which are difficult to clean. Service-life expectancy: 20 years

System 5 Coal Tar Epoxy (225 µ m in total)

Suitable for steel piles

At present used only to coat steel piles and underground steel components

Metallizing (Zinc or Zn/Al) (200 µ m) and Seal coat system (50µ.m)

Could be considered as an option for coating of certain bridges where the steel is in fair condition without too much pitting or other surface defects. Suitable for steel post or attachment brackets on steel handrails.

Metallizing could be performed either in the field or in the shop. Requires SSPC-SP 5 White metal blast cleaning and high surface profile of 50 - 100µm to attain good adhesion to the surface and long service performance. Metallizing could also be performed in winter weather conditions even when the ambient temperatures are marginally below 0˚C. Service life expectancy: 25 years

Hot-Dipped Galvanizing (87 µ m) or Hot-Dipped Galvanizing plus top paint coating (Duplex system).

Suitable for all standard steel handrails and sign support structures. Duplex system is generally specified for sign support columns (prone to salt splash) for additional corrosion protection. Could be considered as an option for coating of bridges when rehabilitation involves deck replacement, especially in locations closer to the galvanizing facility, subject to size limitations.

Hot-dipped galvanizing is a shop operation. This system may be used for recoating steel handrails that were previously painted or galvanized after stripping off the old coatings and preparing the surface by pickling. Long service performance of over 20 years.

Surface Tolerant Paint Coating Systems (Systems for marginally prepared Surfaces – for Overcoating) from MTO Approved List

Suitable for overcoating. Suitable for difficult to access areas and areas cleaned to SSPC-SP3 or SSPC -SP11 or SSPC-SP 12

These systems are surface tolerant coating systems, designed to provide effective barrier protection. However the life expectancy would depend on the degree of surface cleanliness.

Systems 1, 2,3,4 & 5 in the above Table 6.2 correspond to the respective systems in Tables 1-5 of the OPSS 911, April 2003

April 2004 1-50

6.9.2 Comparison of Coating Systems – Technical Characteristics and Performance

Table 6.3 lists the advantages and the disadvantages of the individual coats of the various paint coating system types and metallic coatings (metallizing, hot-dipped galvanizing).

Table 6.3- Advantages and Disadvantages of Coating Systems Used in Ministry projects Coating System Advantages Disadvantages 1) System 1

Low VOC Epoxy Zinc Rich Primer

• More tolerant of poor surface preparation and application than inorganic zinc systems

• usually easier to topcoat than inorganic zinc systems

• spray application preferred, but can be brush or roller applied

• Galvanic protection due to high content of zinc.

• Poor acid and alkali resistance without topcoat

• less solvent resistance than inorganics

Low VOC Water-Based Acrylic Mid and Topcoats

• low odour and user friendly • rapid drying and re-coating • excellent chemical resistance • good corrosion resistance • excellent water resistance (immersion) • good colour and gloss retention • fair abrasion resistance • easy to repaint • good weatherability • Expected life of the system is ≈ 20 yrs

• Low film build per coat • can give dry spray in summer • almost impossible to brush • Poor solvent resistance • Less water resistance • Not surface tolerant • Not recommended for application below 5˚C

2) System 2 Low VOC Epoxy Zinc Rich Primer

• Same as System 1 • Same as System 1

Epoxy Mid-Coat • User friendly • High film build • Excellent salt resistance • Some moisture tolerance (low permeability while curing) • Rapid dry and top coat • Excellent Chemical resistance • Excellent adhesion and flexibility • Surface tolerant

• Poor gloss retention without topcoat

Polyurethane Topcoat • good application characteristics • good chemical resistance • excellent gloss, hardness • excellent UV resistance &

weatherability • excellent flexibility • expected life of the system is ≈ 20 yrs

• not moisture tolerant in high humidity • limited pot life • not recommended for application below 5˚C (slow drying)

3) System 3 Low VOC Inorganic Zinc Rich Primer (alkali silicate)

• fast dry/recoat • excellent solvent resistance • excellent abrasion resistance • gives cathodic protection at scratches

and pin-holes and prevents undercutting

• excellent gloss/colour retention

• Not surface tolerant • no acid resistance • poor alkali resistance • can cause bubbling in finish coats since film

is porous • requires better surface preparation than other

coatings • spray application only

April 2004 1-51

Coating System Advantages Disadvantages Low VOC Water-Based

Acrylic Mid &Topcoats • Same as System 1 • Same as System 1

4) System 4 Low VOC Inorganic Zinc Rich Primer

• Same as System 3

• Same as System 3

Epoxy Mid-Coat • Same as System 2 • Same as System 2

Polyurethane Topcoat • Same as System 2 • Same as System 2

5) System 5 Coal Tar Epoxy

• excellent chemical and solvent resistance

• excellent water resistance • excellent adhesion • excellent abrasion resistance • hard film • expected life of 10 – 15 years

• suitable for coating steel piles • poor gloss retention • chalks in sunlight • will blush when applied in humid weather or

if rained on within several hours of application

• not recommended for applications below 10˚ C • difficult to re-coat due to the continuous

curing mechanism that increases their hardness

6) Hot-Dipped Galvanizing

• good abrasion resistance • not easily damaged • the zinc forms a metallurgical bond

with the substrate giving excellent adhesion

• provides sacrificial protection at pinholes and scratches

• gives thick coating on edges • complete coverage achieved • gives a smooth, even coating • expected life to 20+ years

• coating thickness determined by operational procedures and the thickness and mass of the article

• some fabricated assemblies may distort due to the galvanizing temperatures ( 850˚ F/ 454˚ C)

• Size limitation

Metallizing Zinc/Al 85/15

• provides sacrificial protection at pinholes and scratches

• no solvents, zero VOC • depth of coating can be varied • expected life of 25+ years (with a seal

coat) • can be applied at a lower temperature

(marginally below 0˚ C)

• requires highest level of surface cleanliness and angular profile for proper adhesion

• must be coated soon after blast cleaning • porous surface • sealer is often used

7)

Seal coat • provides additional barrier protection to the metallized coating

• some seal coat systems could be applied even around – 6 ˚ C.

• expected life of the system is ≈ 25 yrs

• needs to be applied as soon as possible before zinc corrosion products form

8) Surface Tolerant Coating System ST 1 Zinc and micaceous iron oxide filled surface tolerant polyurethane Primer

• surface tolerant, suitable for overcoating projects.

• can be applied on to surfaces power tool cleaned to SSPC-SP 3 .

• single component moisture cure • can be applied in cold damp

conditions and even below freezing conditions.

• easy to apply and recoat • Low shrinkage stress

• more experience than most surface tolerant coatings

April 2004 1-52

Coating System Advantages Disadvantages Single component moisture cure polyurethane with corrosion inhibitor and micaceous iron oxide Mid-Coat.

• single component moisture cure • can be applied in cold damp

conditions and even below freezing conditions

• recommended for extremely cold environments

• does not weaken adhesion of old coatings

• not recommended for application directly on to metal surface

Single component moisture cure polyurethane micaceous iron oxide based Topcoat

• single component moisture cure • can be applied in cold damp

conditions and even below freezing conditions.

• good UV, abrasion and weather resistance

• good coverage on edges, threads and cracks due to MIO

Surface Tolerant Coating System ST 2 Aluminum and micaceous iron oxide filled surface tolerant two component epoxymastic Primer 75-125 micron

• surface tolerant, suitable for overcoating projects

• can be applied on to surfaces power tool cleaned to SSPC-SP 3

• low temperature curing • suitable for overlap of most coatings

• may have to use thinners for spray application at low temperatures

• higher shrinkage compared with the moisture cured urethane

The above primer (or an epoxy) Mid -Coat

• same as above for aluminium and micaceous iron oxide filled epoxy mastic.

• for epoxy mid coat- same as System 2

• same as above for aluminium and micaceous iron oxide filled epoxymastic.

• for epoxy mid coat- same as System 2

9)

Aliphatic polyurethane Topcoat

• Similar to System 2

• Similar to System 2

6.9.3 Comparison of Costs for Various Surface Preparation and Coating

Options Table 6.4 provides a breakdown and overall costs per square metre of structural steel for the various coating options/systems (including CESS item and EP item costs).

April 2004 1-53

Table 6.41 – Comparison of Coating Systems Costs –(based on 1998 to 2000 data)

Coating System & Application Method

Surface Preparation Cost/sq.m

$

Cost Per sq.m per Year (approx.)

$

Coating Life Expectancy (approx.)

Years Method Cost

Application Cost/m2

$

Coating Item Total

Cost/.m2

$

Environ-mental

Protection6 Cost/m2

$ Low VOC three coat Paint coating systems2 Full removal & recoating 20 SP 10/

NACE No.2 24.00 20.00 44.00 50 -60 5.00

Zinc/Al 85/15 Metallizing (in the shop) 25 SP 5/

NACE No.1 147.403 - 6.00

Hot -Dip Galvanizing 20-25 SP 8 - - 903/35.04 - 3.60 - 4.50 Overcoating with an approved coating system for marginally prepared surface 6 – 105,7 SP 3 6.00 -

10.00 18.00 24 - 28 20 –30 4.40- 9.60

Overcoating with an approved coating system for marginally prepared surface 8-125,7 SP 118 40.008 18.00 58.00 20- 30 7.40 – 11.00

Water-jetting and recoating with an approved coating system for marginally prepared surface 15-20

SP 12 (WJ2, NV27

Condition) 20.009 18.00 38.00 30- 409 3.40- 5.209

1. The above table reflects comparison of prices for coating systems based on the same simple structure in each case. These unit prices are to be used ONLY for

comparison of the basic coating system cost. The Estimating Office could provide an estimate of cost on a specific structure or could assist by providing historical cost data for use in establishing program values. Special access requirements and traffic control/protection are not included in the cost estimates. Costs of these items including environmental protection costs, depending on their severity, can substantially increase the total coating cost.

2. Low VOC Three coat systems: Low VOC epoxy zinc /epoxy/ polyurethane, Low VOC inorganic zinc/ epoxy/ polyurethane, epoxy zinc/ water-based acrylic/ water-based acrylic and Low VOC inorganic zinc/ water-based acrylic/ water-based acrylic systems.

3. Includes transportation, repair and erection costs. 4. The total cost quoted for hot-dip galvanizing does not include transportation, delivery and erection charges. Transportation and delivery charges are

affected by quantity of panels and distance from job site to galvaniser’s plant. Time to remove, delivery and galvanize would depend on plant workload, but generally, two weeks should suffice.

5. Life expectancy of the original coating is extended by the number of years given in this cell. 6. The figures quoted include environmental protection costs for field application. 7. The use of salt removal agents (e.g. Chlor*rid liquid salt remover, Hold Tight 102) may be necessary during power washing to reduce the level of

chloride ions on the surface to achieve expected life for the coating system/to meet the SSPC-SP12, NV2 requirements. 8. Production rate for power-tool cleaning to SSPC-SP11 is low. Since it is labour-intensive and costly it is not recommended for cleaning large areas. 9. Only a rough estimate at this time, due to lack of field data.

April 2004 1-54

Coating costs and other associated costs for some selected contracts between 1994- 2001 for metallizing, hot-dipped galvanizing and low VOC three coat paint systems, obtained from a MTO Bridge office report7, are reproduced in Table 6.5.

Table 6.5 Coating Cost (Actual) Comparison –Metallizing, Galvanizing and Painting

Contract No.

Type of Coating Total Area Coated in m2

Unit Cost Based on Area of Coated Steel in $/sq.m

Some Details including Other Costs in $

98-45 Metallizing & Seal Coat

1,140 121.10 (Coating item only)

147.10 (Total)

No EP, a) 85,000 Steel Fabrication/Repair, b) 13,000 Transportation c) 17,000 Erection In ER, at Kingston,

95-68 Galvanizing 1,140 93.22 No EP In SWR, at Chatham

94-202 Galvanizing 709 81.56 Includes Access Cost of 9,319.00, In NR, near New Liskeard

98-0076 3 Coat Paint Coating System

34,200 76.11 Includes EP In CR, Total of 7 Bridges in Hamilton, CR

98-207 3 Coat Paint Coating System

1,000 126.60 EP included in CESS, In NWR, near St. Sault Marie

98-270 3 Coat Paint Coating System

5,845 85.44 Includes EP In NR, near New Liskeard

99-0016 3 Coat Paint Coating System

1850 64.92 Includes EP, In SWR, near London

99-0051

3 Coat Paint Coating System

3,046 94.83 Includes EP, In ER, near Lancaster

2000-0047 3 Coat Paint Coating System

2,000 128.12 Includes EP, In CR, near Hwy 9

2000-203 3 Coat Paint Coating System

2,050 122.57 Includes EP, In NWR, near Thunder Bay

April 2004 1-55

7. REFERENCES 1. Kerins P. and Lai, David “Steel Bridge Coating Program- Cost and Options

Study”, Report Number BO-99-01, Bridge Office, Ministry of Transportation, Ontario, 301, St. Paul Street, St. Catharines, Ontario, L2R 7R4, June 1999.

2. Yamashita, M and Misawa, T “ Recent Progress in the Study of Protective Rust layer Formation on Weathering Steel” Paper No 357, Corrosion 98, NACE.

3. Manning, David “ Accelerated Corrosion in Weathering Steel Bridges” Report No.ME-84-03, Research & Development Branch, Ministry of Transportation Ontario, 1984.

4. SSPC, “ Maintenance Coating of Weathering Steel: Field Evaluation and Guidelines”, Report No. FHWA - RD-92-055, Federal Highway Administration, US Department of Transportation, 1992.

5. OPSS 1704, “Material Specification for Paint Coating Systems for Structural Steel”, April 2003, Ontario Provincial Standards. (Distributed by Ronen House).

6. Grant. R., “Evaluation of Materials for Overcoating Marginally Prepared Steel”, Laboratory Report, Chemicals Section, Engineering Materials Office, MTO, Downsview, June 1998.

7. Coomarasamy A. and Lai, David “ Metallizing Steel Girders of Division Street Overpass Hwy 401 Kingston: Technical and Economic Aspects” Bridge Office Report BRO-006, Engineering Standards Branch Bridge Office, Ontario Ministry of Transportation, 301 St. Paul Street, St. Catharines, Ontario, Canada L2R 7R4, December 2002.

8. Joint Surface Preparation Standard SSPC-SP 6/NACE No. 3 “Commercial Blast Cleaning”, September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

9. Joint Surface Preparation Standard SSPC SP 10/NACE No. 2 “ Near –White Metal Blast Cleaning”, September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

10. Joint Surface Preparation Standard SSPC SP 5/NACE No. 1” White Metal Blast Cleaning” September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

11. DSM of Low VOC Paint Systems, Road Authority, (www.roadauthority.com). 12. Ontario Structure Inspection Manual (OSIM Manual), Engineering Standards

Branch Bridge Office, Ontario Ministry of Transportation, 301 St. Paul Street, St. Catharines, Ontario, December 2003.

13. ASTM D 610 - 01“ Test Method for Evaluating Degree of Rusting on Painted Steel Surfaces”, ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoken, PA 19428-2959,USA

14. SSPC-VIS 2, “Standard Method of Evaluating Degree of Rusting on Painted Steel Surfaces”, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

15. Chandler K.A. and Bayliss D.A., Corrosion Protection of Steel Structures, Elsevier Applied Science Publishers, London & New York, 1985.

April 2004 1-56

16. Appleman B. R., “Economics of Corrosion Protection by Coatings”, pp 22- 33, JPCL March 1985.

17. ASM Metals Handbook, 9th Edition, The American Society for Metals International, 1987.

18. SSPC Vol I September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

19. Munger, Charles C., and Vincent Louis D., “ Corrosion Prevention by Protective Coatings”, Second Edition, NACE International, 1440 South Creek Drive Houston TX 77084-4906, 1997.

20. ASTM D 4541- 02, “Standard Test Method for Pull-off Strength of Coatings Using Portable Adhesion Testers”, ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoken, PA 19428-2959,USA.

21. DSM list of Zinc Rich Touch-up Paints, Road Authority, (www.roadauthority.com).

22. Contract Design and Estimating Manual, (CDEM Manual) Prepared by Contract Preparation Office, Ontario Ministry of Transportation, 301 St. Paul Street, St. Catharines, Ontario.

23. Weaver R., “Measuring Dry Film Thickness on Steel I-Beams” Problem Solving Forum, JPCL, November 1999.

24. ASTM 4138 “Standard Test methods for Measurement of Dry Film Thickness of protective Coating Systems by Destructive Means”, ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoken, PA 19428-2959,USA.

25. Zacharia and Lasby, “ Bridge Paint Expert System User Documentation”, Report Number TR/RD/RR-90/09, Project number 8490-8926, Alberta Transportation and Utilities, Research and Development, June 1990.

26. ISO Test Methods a) ISO 8502-2 ‘Laboratory Determination of Chloride on Cleaned Surfaces’. b) ISO 8502-5 ‘Chloride Ion Detection Tube’. c) ISO 8502-6 ‘Bresle Sampling Method’. d) ISO8502-9 ‘Field Method for Soluble salt by Conductivity Measurement’. 27. Bresle Patch test kits, available from many suppliers including R.B. Atlas Inc.,

Toronto, KTA-Tator Inc. USA. 28. Chlor*rid International Inc., PO Box 908, Chandler, Arizona 85244. 29. KTA-Tator, 115 Technology Drive, Pittsburgh, PA 15275, USA. 30. SSPC-TU 4 “ Field Methods of Retrieval and Analysis of Soluble Salts on

Substrates”, August 1, 1998; (This publication has recently been issued as SSPC-Guide 15). 31. SSPC Painting Manual Volume 2 Eighth Edition, 2000, pp723-729. 32. Drisko, Richard W., and Jones, Thomas A., “The Inspection of Coatings and

Linings: A Handbook of Basic Practice for Inspectors, Owners, and Specifiers”, Second Edition, SSPC 03-14, The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA, 2003.

33. Shuang-Ling Chong, Yuan Yao and Rozaruio, M., “Intra-Laboratory Assessment of Commercial Test Kits for Quantifying Chloride on Steel Surfaces”, JPCL Vol. 20, No 8, Aug. 2003.

April 2004 1-57

34. ASTM D 3359-02, “Standard Test Methods for Measuring Adhesion by Tape Test”, ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoken, PA 19428-2959,USA.

35. Kenneth A. Trimber Michael F. MeLampy of KTA-Tator Inc. and George L. Stone of G. L. Stone Enterprises Ltd., “Manual for Technical Discussion of Coating-Related Issues” Technical Material Presented to St.Lawrence Seaway Authority, Ministry of Transportation, 1000 Islands Bridge Commission, Niagara Falls Bridge Commission and New York State Thruway Authority By KTA-Tator Inc. October 1997.

36. Amos Glen A., “Maintenance Painting/Practical Advice" Materials Performance, October 2000 pp 39 - 41.

37. ASTM D 5064 - 01 “Standard Practice for Conducting a Patch test to Assess Coating Compatibility”, ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoken, PA 19428-2959,USA.

38. SSPC-SP 1 September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA. 39. SSPC-SP 3 September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA. 40. SSPC-SP 11 September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA. 41. Neal, Tom W., “ Maintenance Issues and Alternate Corrosion Protection Methods

for Exposed Bridge Steel”, NCHRP Synthesis of Highway Practice 257, Transportation Research Board, National Academy Press, Washington D.C. 1998.

42. AASHTO, “Guide for Painting Steel Structures” American Association of State Highway and Transportation Officials, 444 North Capitol Street, N.W., Suite 249, Washington D.C.

43. OPSS 911, “Construction Specification for Coating Structural Steel Systems”, April 2003, Ontario Provincial Standards. (Distributed by Ronen House).

44. Joint Surface Preparation Standard SSPC-SP12/NACE No. 5 September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

45. Howlett, J. J. and Dunpy, R., “Ultrahigh-Pressure Water Jetting (UHP WJ): A Useful Tool for Deposit Removal and Surface Preparation,” CORROSION/92, paper No. 253, NACE International, Houston, Texas.

46. Appleman B. R., “Critical Aspects of Overcoating” Revised Final Report Prepared by SSPC for BIRL Industrial Research Laboratory, Northwestern University, SSPC Report #R053, Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728, June 1985.

47. Anon, NEPOVERCOAT Standard on Overcoat Field Testing Program for Protective Coatings on Existing Bridges and Salvaged Beam Test Sites, May 19. 1999, Document received from A. Rawson of New Hampshire DOT.

48. Hare Clive H., “Preventing Overcoating Failures” JPCL, November 1997 pp 50-59.

49. SSPC-TU 3 “Technology Update No. 3 Overcoating”, The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

April 2004 1-58

50. Joint Surface Preparation Standard SSPC-SP7/ NACE No. 4 “ Brush-off Blast Cleaning”, September 1, 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

51. Termarust Technologies, 9100 Edison, Anjou (Montreal), Quebec H1J 1T3. 52. Mr. Tharasher’s and Dr. Dorton’s memo to Regional Directors (86-8-19); See

Appendix I. 53. Ontario Traffic Manual Book 7 – Temporary Conditions47, 2001, Queen Printers

of Ontario. 54. Anon "Environmental Guidelines for Structural Steel Coating On Highway

Bridges" 1996, prepared by Ontario Painting Contractors Association (OPCA), Ministry of Transportation (MTO) and Ministry of Environment and Energy (MOEE) (Distributed by Ronen House).

55. SSPC-PA1, “ Paint Application Specification No. 1- Shop, Field, and Maintenance Painting of Steel”, April 2000, SSPC: The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, USA.

56. Structural Manual, June 2002, Design Section, Engineering Standards Branch Bridge Office, Ontario Ministry of Transportation, 301 St. Paul Street, St. Catharines, Ontario (Distributed by Ronen House).

57. Husain, I. And Bagnariol, D., “ Performance of Integral Abutment Bridges”, Report BO-99-04, Engineering Standards Branch Bridge Office, 301 St. Paul Street, St. Catharines, Ontario.

58. CHBDC CAN/CSA-S6-00 Canadian Highway Bridge Design Code, Dec 2000, CSA International, 178 Rexdale Boulvard, Toronto, Ontario M9W 1R3.

April 2004 1-59