marine corrosion protection

1

Corrosion Protection SEO ViandenQuality of Coating Products

Studies by the SEO Construction Departmentof Selected Products

10.04.23Untersuchungen an Korrosionsschutzprodukten für den Stahlwasserbau / C.Tonino 2

Introduction

• Purpose of the studies:

Determining the quality of the coating systems for difficult corrosion protection in hydraulic steel structures.

Comparison of various corrosion protection products.

Statements concerning the durability of the protective effect of the various corrosion protection products.


Main Topics

• Function of the coating materials

• Properties of the coating materials

• Test methods

• Water diffusion test (description/results)

• Findings


Function of the coating materials

• Coating materials are supposed to maintain a barrier function between steel (substrate) and water, which lasts as long as possible, in order to prevent corrosion damage.

• For this purpose, they must be as watertight as possible .


Properties of the coating materials

• The polymer structure of the coating materials results in a greater or lesser porosity of the coating film.

• This permits water to penetrate as a function of the type and quality of the binder, the pigments/fillers, and solvent content, etc.

• Coatings can be regarded as a permeable membrane (more or less solid, cross-linked polymer film).

• Diffusion depends on the structure and thickness of the covering layer .


Diffusion and its consequencesFunctional mechanism

• Corrosion residues and salts on the steel surface, which strive to become diluted, attract water through the coating (e.g. iron sulfate).

• Salt solutions form on the steel surface and this results in a concentration gradient between the outside and the inside of the coating.

• An osmotic pressure develops, which allows more and more water to flow through the coating in the direction of the substrate (steel).

• Bubbles filled with water form on the coating, leading to the detachment of the coating and finally to its bursting.

• This leads to local corrosion damage at first, later to large-area corrosion damage (pitting, rust, etc.)


Material transport through coatingsConsequences for the coating

Water absorption, caused by osmosis, depends on the binder and the pigmentation.

→ it brings about swelling of the coating a decrease in cohesion and,

with that, a decrease in tensile strength perpendicular to the surface (cohesion rupture)

→ it influences the chemical bonding of the coating to the substrate Decrease in adhesion Bubbles or loosened areas occur.


Practical example:

Ball valve pressure plate TU2, coated in 1999, partially stressed (with Sika Poxitar SW 200-250 µm), findings after eight years


Other factors can influence the diffusion process:

• Salt residues, dust, dirt on the substrate

• Solvents in the coating

• Water quality

• Binder residues, which have not been cured

• Primers, base coats


The following counteract the diffusion process:

• Diffusion resistance of the product

• Layer thickness of the product

• Adhesion strength of the coating

• Cleanliness of the substrate surface


Test methods used for quality studies of substrate and coating material (at SEO)

Substrate quality: -Visual comparison with standardized comparison samples,

-Salt concentration studies ,

-Examination for dust residues ,

-Measurements of the roughness of the steel surface

• Tensile Adhesive Adhesion testing equipment (tensile force perpendicular strength : to the die that is glued on)

• Diffusion resistance: Δ-T Test


Diffusion resistance / Δ-T Test:Test arrangement (thermodiffusion)


Diffusion resistance / -T TestOf central importance for corrosion protection

Parameters determining the diffusion rate of water through the coating to be tested:

• Temperature (Gradient,Difference)

• Layer thickness

• Quality of the coating

• Application of the coating

Assessment criterion :

Diffusion period in days until bubbles appear on the coating surface


Criteria in similar tests by the main RWE Laboratory

Studies for the selection of products for coating the pressure lines 1 and 2 of the PS power plant Vianden 1997/98)

• A coating should withstand the tube test for approximately 20 days (at 40/10°C) without forming bubbles, in order to be able to achieve a resistance of at least 20 years (experience of RWE laboratory).


Coating after diffusion of water(in the thermodiffusion test)

Example:Tenaxon 555CS (version 2007, epoxy, solvent-based,

average layer thickness 500 µm)Outside bath temperature 40°C/inside temperature

in experimental tube 10°CTime period until the first bubbles appear: 2 days


Coating after diffusion of water in the thermodiffusion test (-T Test)

Example:

Caparol Disbon 705

Polibrid coating

600 to 1500 µm

Time period until bubbles form

approximately 10 days in the

region of 700 µm


Comparison of test tube test / WDD test according to DIN EN ISO 6270

(Water vapor (40°C) applied to plate, back side: air (20-25°C), layer thickness 500 µm, bubbles form after approximately 1 year in the case of ICOSIT)

SIKA ICOSIT 500 SW ACOTEC HUMIDUR ML


Diffusion period in days until the appearance of bubbles on the coated surface in relation to the layer thickness in µm

(Selection from more than 40 different tests and products until now)

Steam diffusion test 40/10

0 10 20 30 40 50 60 70 80 90 100

Humidur ML 1999

Humidur ML 2004

Humidur ML 2005

Humidur ML 2005 better

Humidur ML TU 5 (2005)

Humidur ML 2006

Humidur ML + (Carboline Primer) 2007

Humidur ME (grau) 2007

Aquapure Fast

Aquapure Slow

Aquapure Schnell-Slow

Icosit SW 500

Inertol Poxitar SW

Icosit Poxicolor SW

Icosit 299 HS

Agopur Elastik

Agrovan 209

Ceram Kote SPG

Epiter 130 TF

Permacor 136 TW

Softturb

International Paint Interzone 954

JAK Versapox

LECO UWB-E 48

Tenaxon 555 CS (coated on May 4, 2007)

Co

ati

ng

pro

du

cts

days

0 500 1000 1500 2000 2500

Value in micrometers

Days

Average in micrometers


Conclusions from the Table: Durability of the corrosion protection

Based on the results found in the diffusion test and the previous results from the RWE laboratory tests, there are only

• a few coating materials that pass the test over a period of more than 17-20 days, at an average layer thickness of 500 µm, without forming bubbles:

• HumidurML from 1999 at 400 µm 17 days (with 2 mm tube)• (More recent batches, however, show lower values in spite of repeated

complaints raw materials for the curing agent have been changed)

• Aquapure HR: at 480 µm, more than 90 days without forming bubbles

• Interzone 954: at 350 µm 45 days (solvent-based)

• CeramKote 54: at 500 µm more than 40 days without forming bubbles

• Epiter 130 TF: at 400 µm 21 days (solvent-based)

• These products will offer long-term corrosion protection if applied correctly.


Findings

• The coating will last longer if its diffusion resistance is higher.

• Water is kept away from the substrate as long as possible.

• Any contaminants that might be present will react more slowly.


Selection criteria for application in the various water power plant sectors:

• Long durability of the corrosion protection

• Application method

• Ease of repair

• Environment and health


Application methods

For application in accordance with good practice, the following criteria should be observed:

- Application temperatures (substrate, coating, atmosphere)

- Equipment (spraying, brush-coating)

- Processing time (pot life)

- Ability to apply multiple coatings (multiple layers, repairs)


Environment and Health

The products selected must not contain any materials that are harmful to the environment and to health:

(VOC guideline and REACH regulations)

• no solvents

• no polycyclic aromatic hydrocarbons

• no carcinogenic materials

• n components that contaminate water


Advantages and disadvantages of the aforementioned products in comparison with one another:

Humidur ML 1999

5/1weight

Aquapure HR

1/1

Interzone 954

4/1vol

EPITER TF 130

4/1weight

Ceram-Kote54

6.7/1weight

Diffusion resistance

in days for 500-600 µm

20 ~ >90 ++++

(for 300µm 35days.)

45 ++ 21 ~0 >40 ++

Solvent content none none VOC 130g/l VOC 28g/l VOC168g/l

R groups R21/22/23/24/25/34/36/

38/39/43/45/48/51/52/53

/68/

R45 carcinogenic

R34/43/20/22/36/38/

43//51/53

R10/11/20/21/22/34/

36/37/38/43/51/52/5

3/66

R11/20/36/37/38/43/2

1/22/34/37/51/53/66/6

7/

Allowed for drinking water no yes no no no

Max. layer thickness

Min. layer thickness /

370µm

/

350µm

125µm

450µm

/

450µm

125µm

450µm

Adhesion strength N/mm2 >20 >20 >20 >15 /

Processing

Pot life at 18°C in min

Manual processing

40

good

30

very good

90-120

poor

45

good very poor


Next Steps

• Detailed study of the Aquapure HR und Interzone 954 by the RWE laboratory; comparison with HUMIDUR ML (1999/2007)

Further studies of other productse.g. products that are being used by EDF in France

marine corrosion protection

Education

coating surface

coating film

coating application

polibrid coating

coating cleanliness

coating water absorption

coating materials properties

coating materials results