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GENERIC COATING TYPES

Polyester and Vinyl Ester Coatings

olyester and vinyl ester resin-based linings are known fortheir solvent and chemical

resistance. The different resins inthese linings have broad resistanceranges, with acid resistance being amajor strength. Some of the specificresins resist 1 or more chemicals ortypes of chemicals better than otherresins, so systems often are fine-tuned by the choice of resin for aparticular chemical environment.

Esters are the reaction product of an organic acid and an alcohol.Polymers used in this class of mate-rials are the unsaturated polyestersformed by reaction of unsaturateddibasic acids and dihydric alcohols.Styrene or a similar vinyl-typemonomer is used to cross-link the resin and form the film. Thepolymerization is initiated by a cata-lyst, with the reaction by free radicaladdition, which is a chemical reac-tion mechanism unique to this classof coatings.

The word “lining” in the coatingsindustry is commonly defined as amaterial used to protect the insidesurface of a tank, vessel, or similarstructure from highly corrosive orpotentially highly corrosive expo-sures. Linings can be monolithic sys-tems or built-up systems. Because oftheir typically thick application anduse in severe chemical conditions,polyesters and vinyl esters normallyare referred to as linings. They offergood adhesion to most substrates,although most applications are onsteel or concrete.

These linings include several sys-tems varying in thickness, type of

fillers and reinforcement, and appli-cation method. For each lining sys-tem, various polyester and vinylester resin bases are used to achievethe desired chemical resistance.

History of DevelopmentSince the 1960s, polyester and vinylester linings have been used extensively for their high chemical resis-tance. They previously had beenused in mortars for chemical-resis-tant brick linings and fiberglass-rein-forced plastic (FRP) structures suchas tanks, pipes, and ducts, so theiruse in protective linings is a naturalextension of their broad chemical re-sistance properties.

Early linings were reinforced withchopped fiberglass strands or wovenfiberglass cloth (woven roving). Sili-ca and other particulate fillers wereincorporated to enhance physical

properties and minimize curingshrinkage, the release of heat aftermixing, and a high coefficient ofthermal expansion compared to thesubstrate. These linings were ap-plied by trowel and roller up to 1⁄4 in.(6 mm) thick.

As these linings were developed,flake fillers were added to increaseresistance to permeation by watervapor. This property is important forimmersion or wet service at elevatedtemperatures. Glass and mica flakeswere used to extend the servicetemperatures of the linings in hot,aqueous environments. This type oflining can withstand immersion tem-peratures of 180 to 212 F (82 to 100C) at thicknesses of 60 to 150 mils(1.5 to 3.8 mm).

Thinner, spray-applied systemswere formulated to reduce materialcost and increase application rate.

P

88 / Journal of Protective Coatings & Linings

Table 1Properties of Lining Fillers and Reinforcements

Silica Fillers Most used, good permeation resistance, low cost

Carbon Fillers Electrical conductivity or fluoride resistance

Hard Mineral Fillers Increased abrasion resistance

Fiberglass Chopped Mat Good chemical resistance

Fiberglass Woven Cloth Strong, bidirectional reinforcement

Fiberglass "C" Grade Veil Best chemical resistance

Synthetic Reinforcements Where fluorides would attack glass

Glass Flakes Best permeation resistance when aligned

Mica Flakes Good permeation and chemical resistance

Tables courtesy of the author

by William R. Slama Master Builders, Inc.

Lloyd M. Smith, General Editor, Corrosion Control Consultants and Labs

Copyright ©1996, Technology Publishing Company

Spray-applied systems of 2 coats, 15 to 20 mils (375 to 500 microme-ters) each, proved to be useful formore economical chemical-resistantapplications at temperatures up to130 F (55 C). Eight to 10 mils (200 to250 micrometers) per coat appearsto be the practical minimum thick-

an unsaturated monomer (usuallystyrene) to form the resin compo-nent. By addition of a peroxide cata-lyst, a free radical addition reactionoccurs that transforms the liquidresin into an infusible solid film. Afree radical is a species that has anunpaired electron and is so reactivethat it only has a transient existence.The free radical polymerization reac-tion occurs at the carbon-carbondouble bonds (C=C) of the unsatu-rated moieties. Although themonomer may be volatile in its liq-uid state, it is the cross-linkingagent, and it is incorporated into thefilm. Thus, these systems theoretical-ly are 100 percent solids formula-tions. Evaporation is not required asin solvent-borne systems.

Polyester prepolymers are pro-duced by a condensation reaction of organic acids and polyols. Thechoice of reactants will establish the resulting polymer properties—mechanical properties, thermal sta-bility, and chemical resistance. Com-monly used polyols include bisphe-nol A, neopentyl glycol, andpropylene glycol. The most commonorganic acid reactants are isophthalicacid, orthophthalic anhydride,terephthalic acid, fumaric acid, andmaleic anhydride.

Vinyl ester resins are a type orsubset of polyester resin. Vinyl esterprepolymers are formed by reactionof epoxy resin (polyol) with acrylicor methacrylic acid, which containsthe vinyl group. Bisphenol A andnovolac epoxies generally are used.Novolac-based vinyl esters are morereactive than bisphenol A and pro-duce polymers with greater thermalstability and chemical resistance.

General Performance PropertiesStrengths of Polyesters and Vinyl EstersThese resins generally are low inviscosity and cure quickly at ambi-

ness for polyester- and vinyl ester-based coatings.

General Chemical Characteristicsand VariationsThis group of linings is based on un-saturated thermosetting resins (asprepolymers) that are dissolved in

MAY 1996 / 89continued

Table 2Chemical Resistance Ratings for Polyester and Vinyl Ester Linings

Generic Resin Type

Chemical ISO BIS-A CHLOR VINYL-E NOV-VE

Acetic Acid–10% D1 C1 C1 C1 A1Acetic Acid–100% E2 D2 D2 D2 D1Acetone N N N N C2Ammonium Hydroxide–20% N E1 N E1 E1Ammonium Nitrate A1 A1 A1 A1 A1Benzene D2 D1 D1 E2 D1Chromic Acid–10% N E1 C1 N E1Formaldehyde A1 A1 A1 A1 A1Formic Acid E2 D1 D1 E1 D1Gasoline–Unleaded A1 A1 A1 A1 A1Hydrochloric Acid–10% E1 A1 A1 A1 A1Hydrochloric Acid–37% E2 D2 D2 D1 D1Hydrofluoric Acid–10% * E1 D1 D1 D1 D1Kerosene A1 A1 A1 A1 A1Methylene Chloride N N N N E2Methyl Ethyl Ketone E2 E2 E2 E2 D2Nitric Acid–10% D2 B1 A1 C1 A1Nitric Acid–60% N D1 D1 N D1Oils A1 A1 A1 A1 A1Phosphoric Acid–85% A1 A1 A1 A1 A1Sodium Chlorate B1 A1 A1 A1 A1Sodium Hydroxide–10% * N D1 N D1 D1Sodium Hydroxide–50% * N C1 N C1 C1Sulfuric Acid–50% B2 B1 A1 B1 A1Sulfuric Acid–75% E2 E1 E1 E1 E1Toluene N E2 E2 E2 E1Trichloroethylene N E2 E2 E2 E1Vinegar (Acetic Acid–3%) A1 A1 A1 A1 A1

These ratings are typical for polyester and vinyl ester linings and reflect the maximum recommended temperatures. Maximum temperature for any given lining type may be lower depending on lining thickness and permeation resistance. See Table 3.

Resin AbbreviationsISO IsophthalicBIS-A Bisphenol-A FumarateCHLOR ChlorinatedVINYL-E Vinyl EsterNOV-VE Novolac Vinyl Ester

Ratings1 Good for immersion or constant flow2 Limited to spillage or secondary containmentA Good to 200 F (93 C)B Good to 180 F (82 C)C Good to 140 F (60 C)D Good to 120 F (49 C)E Good to 100 F (38 C)N Not Recommended

*Exposed lining surface requires carbon filler or synthetic veil



ent temperatures without post cur-ing. They offer excellent adhesionand high strength.

Polyesters and vinyl esters areknown for their chemical resistance,although most are better in acidicenvironments than in strong alkalineconditions. (Alkaline solutions attackthe ester linkage, reforming thepolyol and a salt of the carboxylic

acid.) They are resistant to organics,including solvents, as well.

Polyesters and vinyl esters areused in applications that require resistance to aggressive chemicalsand elevated temperatures as highas 212 F (100 C) wet or 350 F (177C) dry.

Uses include tank linings; floorlinings; secondary containment lin-

ings; and coatings for structuralsteel, walls, and ceilings.

Limitations of Polyesters andVinyl EstersThese resins undergo high shrinkageand give off heat during cure. Theheat and the shrinkage produce atrapped tensile strain (pre-stress)that can lead to cracking or disbond-ment, especially at very low operat-ing temperatures. If not reinforced,the resins are brittle.

Modification by addition of fillersor reinforcement to increase flexibili-ty usually reduces resistance tochemicals and decreases thermal sta-bility. The resins have a high coeffi-cient of thermal expansion, so rein-forcement is critical.

The resins generally are inhibitedby contact with oxygen during cure.This inhibits surface cure, and thetop (air-exposed) surface does notcross-link completely, significantlyreducing chemical resistance. Forthick linings, this usually is not acritical factor. However, for thincoatings (less than 40 mils or 1 mm),and for maximum chemical resis-tance, it may be critical. The tenden-cy and degree of sensitivity to air in-hibition vary greatly among thedifferent resins in this group. Paraf-finic additives often are incorporatedin lining topcoats to reduce air inhi-bition by forming a film over thesurface before cure.

Proper formulation is required totake advantage of the chemical resis-tance properties of these materialswhile minimizing potential pitfalls.

Lining Types and ComponentsUnreinforced Filled SystemsThese products use a particulatefiller to extend the base resin. Silicafillers, including graded, washed,and dried sands, along with crushedor fumed silica flour and other mineral fillers, are used. The pre-blended fillers usually are furnished



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as a separate component referred toas an aggregate.

At the time of application, thehardener (or activator) is first addedto the resin component, and the 2are mixed thoroughly. Next, the aggregate or filler is added andmixed until uniform. The compoundis spread on the substrate, such as a floor, and troweled to the desig-nated thickness. A typical thicknessis 1⁄4 in. (6 mm).

A high fill ratio (5 to 10 parts fillerto 1 part resin by weight) is used toreduce cost, minimize curing shrink-age, and reduce the coefficient of thermal expansion of the film. Because this combination tends to be very rigid and brittle, flexibiliz-ers may be added to the resin, re-ducing the chemical resistance. Useof these products generally is limitedto concrete floors. They have high resistance to abrasion damage. Theyare relatively rigid, however, and

will crack over moving cracks in the concrete.

Alternatively, this type of productmay be installed by the broadcastsystem. There are several variations,but the most common method in-volves application of the resin/hard-ener mix, which is poured directlyonto the concrete surface andspread by squeegee or roller.

Immediately, a filler is broadcastonto the surface by hand or me-chanical means. It usually is appliedto excess, until it no longer sinksinto the resin and no resin is visible.After the resin cures, the surface isswept to remove the unbonded, ex-cess filler.

This process may be repeated sev-eral times, depending on the thick-ness desired. Finally, 1 or more ad-ditional coats of the resin areapplied to smooth and seal the sur-face. This system is generally 1⁄16 to 1⁄4in. (11⁄2 to 6 mm) thick.

Reinforced Composite LiningsFiberglass reinforcements are usedextensively to add strength to a lin-ing. In addition to increasingstrength and resistance to cracking,they greatly reduce curing shrinkageand coefficient of thermal expan-sion. The relatively high modulus ofelasticity of fiberglass and its abilityto be bonded by the resin make itvery effective for linings.

In addition to fiberglass reinforce-ment, one or more layers containfillers such as silica, carbon, or hardmineral particles. These fillers areespecially necessary for elevatedtemperature service in aqueous envi-ronments. Typical system construc-tion for several lining types is shownin Figs. 1 and 2. Thickness generallyranges from 1⁄8 to 1⁄4 in. (3 to 6 mm).

Most systems use preformed layersof chopped fiberglass strands orwoven fiberglass “cloth.” During lining installation, the fiberglass is



Copyright ©1996, Technology Publishing Company MAY 1996 / 93


saturated with catalyzed resin androlled thoroughly to fully wet the in-dividual glass strands and removeair bubbles.

A combination of chopped fiber-glass strands and catalyzed resinalso can be spray-applied using achopper gun. Continuous strands offiberglass called roving are choppedinto short strands, typically 1 to 2 in.(25 to 50 mm), and injected into thecatalyzed resin stream exiting thegun. Though effective for some ap-plications, this method relies heavilyon operator expertise to maintainreasonable control of thickness.

Chemical-grade fiberglass veilcalled “C” veil is more resistant to attack and normally is used as a top reinforcement layer. However,synthetic fiber reinforcements (e.g.,polyester) are used on the top surface instead of the fiberglass veilfor environments such as hydrofluo-ric acid or hot caustic that would attack glass.

Flake-Reinforced Linings and CoatingsFlake reinforcement is most effectiveat providing a barrier to permeationof the lining. The aligned flakesmake the path of water or othercontaminants through the resinmuch longer. Since the flakes arenot permeable, water moleculesmust travel a much greater distance,and the resistance of the compositeis greatly increased. This barrier ef-fect is important for high tempera-ture immersion service.

Trowel-applied glass flake-rein-forced systems provide the highestpermeation resistance since largeglass flakes up to 1⁄8 in. (3 mm) in diameter can be incorporated (Fig. 3). These linings are rolledafter application to minimizetrapped air and assist in flake align-ment. These systems normally areapplied in 2 or more layers. Thick-ness ranges from 60 to 160 mils (11⁄2

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MAY 1996 / 95

to 4 mm) for temperature service upto 200 F (93 C).

Smaller glass or mica flakes areused in spray-applied systems. Theflakes, though not as well aligned,still provide a high degree of rein-forcement and increased permeationresistance. Spray application reducesapplied cost. Spray-applied systemstypically withstand immersion tem-peratures of 130 to 150 F (54 to 66C) when applied in 2 to 3 coats at30 to 80 mils (3⁄4 to 2 mm). In nonim-mersion conditions, flake-reinforcedpolyester linings can withstand tem-peratures of 300 to 350 F (149 to 177C), while vinyl esters can withstand

350 to 400 F (177 to 204 C). Thinnersystems of 2 coats at 20 mils (1⁄2 mm)normally are recommended for mild,nonimmersion applications (Fig. 4).

Crack-Bridging LiningsChemical-resistant polyester andvinyl ester linings are somewhatrigid but function well on steel sub-strates. However, they have very lit-tle, if any, ability to remain continu-ous without cracking or to bridgecracks in concrete substrates thatopen after the lining is installed.That is because the localized strainover the crack (the change in widthdivided by the original width) is ex-

Troweledfilled topcoat

Resin-saturatedfiberglass cloth

Troweledfilled basecoat

Primer

Fig. 1 - Fiberglass cloth-reinforced lining with filled basecoat and topcoat

2 resin coats

Surface mator veil

2 layersfiberglass mat

Troweledfilled basecoat

Primer

Fig. 2 - Fiberglass mat-reinforced lining with silica-filled basecoat


tremely high and can cause a crackto propagate through the lining.

Making the resin more flexible isnot a valid option, since that wouldreduce the chemical resistance. Toprovide the high chemical resistanceof these linings and bridge crackmovements in concrete substratescaused by shrinkage or thermalmovement, special engineered com-posite linings have been developed.

These systems incorporate a verylow modulus (soft) basecoat ormembrane with a tough, high modu-lus, fiberglass-reinforced layer to“disengage” the lining from the sub-strate in areas of high strain, such as

over moving cracks. The basecoatmay be neoprene, urethane, orheavily flexibilized epoxy. In thisway, the localized crack movementresults in high shear deformation inthe soft basecoat, and the high mod-ulus spreads the strain over a widearea (4 to 20 in. or 102 to 508 mm)of the chemical-resistant top layers.The desired, highly resistant lininglayer is applied over this decouplingsystem (Fig. 5). Essentially, the crackdisplacement is spread over a 6- to12-inch (152- to 305-mm) width oflining so that the strain can be toler-ated without cracking.

Other linings or lining systems,

even fiberglass-reinforced linings,will crack when substrate cracksopen as little as 2 mils (50 microme-ters). Composite crack-bridging systems can accept crack movementup to 120 mils (3 mm) withoutcracking.

Lining FormulationEven though the lining formats (re-inforcement types and applicationsteps) and the base resins of poly-ester and vinyl ester linings from dif-ferent manufacturers may be thesame, individual lining ingredientsand performance may vary. This isbecause of the many interactive ele-ments that make up the final liningor coating.

The resin and monomer combina-tion must contain promoters to helpinitiate the reaction when the cata-lyst is added. Inhibitors are neces-sary to maintain a useful shelf lifewithout pre-hardening or gelation of the resin. Flexibilizers may reducebrittleness, and pigments may pro-vide color for appearance or to distinguish between coats during application.

Thixotropic agents and polaragents are combined to build thesag resistance necessary to holdthick layers on vertical or overheadsurfaces before curing. Fillers, flakes,or reinforcements are essential to es-tablish needed physical propertiesand reduce permeability. Wettingand coupling agents are used tomaintain adhesion between the resinand the surfaces of the fillers. Level-ing or flow agents may be added toprovide smoother surfaces. Proper-ties of key fillers and reinforcementsare shown in Table 1.

Silica filler blends are the mostcost-effective for building thicknessfor durability, permeation resistance,and reduced shrinkage and coeffi-cient of expansion.

Carbon fillers and synthetic fiberreinforcements are used where silica



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Troweled and rolled,glass flake-reinforcedbasecoat and topcoat

Primer

Fig. 3 - Troweled glass flake lining

Spray-applied,flake-reinforced

basecoat and topcoat

Primer

Fig. 4 - Spray-applied, flake-reinforced lining


would be chemically attacked. Carbon also is used to produce elec-trical conductivity on lining and flooring surfaces to dischargestatic electricity.

To increase abrasion resistance,hard mineral fillers such as alu-minum oxide are incorporated.Glass fibers are most often used inthick lining systems in the form ofchopped strand mat, woven cloth,and chemical grade surface veil.Flake fillers are most efficient in re-ducing permeation.

Physical And Performance Properties Shrinkage and Coefficient ofThermal ExpansionPolyester and vinyl ester resins ex-hibit relatively high shrinkage duringcure. On a volumetric basis, 8 to 10percent shrinkage during cure is typ-ical for the neat resin with no fillers,additives, or reinforcements. The co-efficient of thermal expansion is 20 to 40 x 10-6 in./in./F (36 to 72 x 10-6mm/mm/C). Because the linings



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Chemical-resistant topcoat

Fiberglass mat-reinforced layer

Flexible low modulus

basecoat

Primer

Fig. 5 - Crack-bridging lining system

Cold Wall Effect

Lining Steel Substrate

Liquid@180 F (82 C) Ambient Air

148 F (64 C)

70 F (21 C)

180 F(32 C)

150 F(66 C)

30 F(-1 C)

∆P ∆T

Fig. 6 - Greater water pressure at liquid-lining interface than at lining-steel interfaces drives water to lining-steel interface, possibly resulting in delamination.



are applied to rigid steel and concrete substrates, which have co-efficients of thermal expansion ofabout 6 x 10-6 in./in./F (11 x 10-6mm/ mm/C), fillers and rein-forcements are important to mini-mize the stresses developed in thelining during cure and created bychanges in temperature.

Given the thickness and rigidity ofthe substrates, the lining must ac-commodate thermal expansion andcontraction of the surface to which itis applied. The lining must undergothe imposed strain and resultingstress without cracking, delaminat-ing, or shearing from the substrate.The coefficient of thermal expansionfor complete linings ranges from 12 to 15 x 10-6 in./in./F (22 to 27 x10-6mm/mm/C) for filled, reinforcedsystems and large glass flake-rein-forced systems to more than 20 x10-6 in./in./F (36 x 10-6 mm/mm/C)for spray-applied, mica-filled sys-tems. Fortunately, these systems nor-mally have enough flexibility to ac-commodate the thermal strains.

AdhesionThese systems have good adhesionto carbon steel, many other metals,and concrete. However, a coarse,angular abrasive blast profile is im-perative on metallic substrates tohelp mechanically lock the coatinginto the surface so that it will with-stand the stresses caused by curingand temperature changes.

FlexibilityThe chemical-resistant base resinsused to produce these linings arerelatively rigid, with maximum elon-gation of 2 to 5 percent. Some spe-cialty resins have higher elongation,up to 10 percent, but, generally, aselongation and flexibility go up,chemical resistance and thermal sta-bility are reduced.

Adding fillers and reinforcementsto strengthen and increase perme-ation resistance greatly reduces the

elongation capability of the liningsystem. The amount of elongation orimposed strain that will crack theselinings is typically from 0.25 to 0.5percent. Manufacturers provide rec-ommendations for the design ofequipment to be lined with regardto the maximum strain or amount offlexing that their linings can reliablytolerate. Normal design for most car-

bon steel substrates, however, usual-ly will be rigid enough, with maxi-mum surface strains of 0.07 to 0.1percent. Special emphasis should beplaced on areas of high local strainor bending. These include floor-to-wall junctions of tanks and bottomareas with poor support. Certaintypes of storage tanks with lap-weld-

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ed bottoms require special attentionin designing and applying the lining.Where tank bottom support is in-complete, grouting may be recom-mended to minimize flexing. Con-crete, as a substrate, is much lessflexible. Aside from crack move-ments, concrete strain will never ex-ceed 0.01 to 0.02 percent.

Chemical ResistanceAs previously stated, polyester andvinyl ester linings are used widelyfor their resistance to a broad rangeof chemicals. Isophthalic polyestersgenerally have poorer chemical re-sistance than vinyl esters and morechemical-resistant polyesters. How-ever, isophthalic polyesters are lessexpensive than vinyl esters andother polyesters and may give ade-quate performance in a specific ex-posure environment.1 Bisphenol Afumarate resins have the advantageof very broad resistance, includingstrong alkaline environments. Chlori-nated polyesters, while not good inalkaline conditions, excel in strongmineral and oxidizing acids. Chlori-nated polyesters are the best choicefor strong chromic acid. Vinyl estersalso offer resistance to a wide pHrange and high temperatures. No-volac and other high molecularweight vinyl ester resins offer betterstability in high temperatures andimproved resistance to sulfuric acid.

Table 2 shows typical chemical re-sistance capabilities for a range ofchemicals and resin types. The tem-peratures shown are maximums, andthe type (thickness and construc-tion) of lining may reduce the maxi-mum temperature capability of thelining. Even though generalizationscan be made for these linings basedon the type of resin and reinforce-ment, performance will not be uni-form because each product is a proprietary formulation. Consult the lining manufacturer for specificrecommendations, and perform in-service coupon tests, if possible.

When elevated temperature serviceis involved, the best test method isan application directly to the vessel wall so that the effect of thethermal gradient on permeation is evaluated.

Permeation ResistanceBecause polyester and vinyl esterlinings may be placed in immersion

at elevated temperatures, high per-meation resistance is necessary toavoid failure by blistering or loss ofadhesion. Permeability is reduced byaddition of reinforcements andfillers. The type and amount of fillerare important to the lining’s perme-ability. Large glass flakes, troweledand rolled for orientation parallel to

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the substrate, are most effective inreducing permeability. Silica, carbon,and other particulate fillers are effec-tive because of the large amountthat can be added to the resin, re-sulting in the ability to build a thick-er layer. Fiberglass, in various forms,though very effective for reinforce-ment, does little to reduce perme-ation because of the small amountthat can be used (5 to 20 percent byvolume).

Permeability and lining permeancefor various lining types are shown inTable 3. Permeability is the propertyof the material regardless of thick-ness, and permeance (permeabilitydivided by thickness) is the propertyof a lining at a given thickness.These properties are measured usingthe procedure outlined in ASTM E96, Test Methods for Water VaporTransmission of Materials.

Note the great difference in per-meability using different fillers.Aligned glass flake fillers are by farthe most effective in reducing per-meability and, in turn, increasingability to withstand higher tempera-ture immersion service.

The maximum wet service temper-ature tends to follow the lining per-meance. This temperature is best es-tablished by testing the lining inaccordance with ASTM C 868, TestMethod for Chemical Resistance of Protective Linings. This method is for testing by the one-sided immersion or Atlas cell test. It is animportant laboratory test for evalua-tion of linings to be used in aqueousenvironments at elevated tempera-tures because of the “driving force”created by the temperature gradientwithin the lining—cooler at the sub-strate than at the immersed surface

(Fig. 6). Commonly referred to asthe “cold wall effect,” this can causecondensation of water at the sub-strate surface, resulting in corrosionand blistering.

Uses of Polyesters and Vinyl EstersPolyester and vinyl ester lining sys-tems are used for top to bottom pro-tection of industrial plants andequipment, especially where acid ororganic chemicals are present. Theseuses include protective, spray-ap-plied coatings for ceilings, walls,hoods, ducts, and tank exteriors; in-terior tank linings; reinforced floor-ing for process spillage areas; andtrenches, sumps, and secondarycontainment surfaces.

There are many applications forthese products throughout the



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Table 3Permeability of Various Polyester and Vinyl Ester Linings

Permeability Thickness Permeance Max. wetFiller/ perm in. mils perms* Relative service

Resin Reinforcement Application (g/Pa•s•m) (mm) (g/Pa•s•m2) permeance F (C)

Novolac 1/8 in. (3 mm) Trowel & roll 0.00011 70 0.0016 1 200+Vinyl Ester Flake glass 2 coats (160E-15) (1.8) (9.15E-11) (93+)

Bisphenol A 1/8 in. (3 mm) Trowel & roll 0.00022 70 0.0031 2 200+Polyester Flake glass 2 coats (319E-15) (1.8) (1.77E-10) (93+)

Novolac 1/64 in. (0.4 mm) Spray 0.00100 54 0.0185 12 150Vinyl Ester Flake glass 3 coats (1.4 E-12) (1.4) (1.06E-09) (66)

Bisphenol A Silica filler Trowel/roll & 0.00310 150 0.0207 13 160Polyester fiberglass cloth trowel topcoat (4E-12) (3.8) (1.18E-09) (71)

Bisphenol A Silica filler Trowel basecoat 0.00440 125 0.0352 22 160Polyester fiberglass mat mat/resin coats (6E-12) (3.2) (2.01E-09) (71)

Bisphenol A Mica flake Spray 0.00160 35 0.0457 29 130Polyester 2 coats (2E-12) (0.9) (2.61E-09) (54)

Bisphenol A Fiberglass mat Roller-applied 0.00780 60 0.1300 81 120Polyester fiberglass mat (11E-12) (1.5) (7.44E-09) (49)

Isophthalic Mica flake Spray 0.00300 18 0.1667 104 120Polyester 2 coats (4E-12) (0.46) (9.54E-09) (49)

* Perm = Grains of moisture/hr/ft2/in. Hg (g/Pa•s•m2)

NOTE: “E” in the metric conversions for perms and perm inches stands for exponent (e.g., 9.15E-11 is the same as 9.15 x 10 -11).

Lining Type



chemical process industry and in avariety of other industries that han-dle corrosive chemicals. Examplesare given below.• In primary metals plants, theseproducts may serve as reinforcedlinings to protect concrete floors,foundations, and trenches from acidsused for pickling. • The pharmaceutical industry usesreinforced vinyl ester for sanitaryprotection of process floors exposedto acid and organic solvent spills.Special crack-bridging versions areused for truck unloading areas andsecondary containment basins.• For more than 25 years, the powerindustry has used flake-reinforcedand fiberglass-reinforced linings forscrubbers, tanks, ducts, and stacksto protect critical flue gas desulfur-ization (FGD) equipment for long-term service.• The waste treatment industry con-tinues to use these systems for stor-age and neutralization tanks, un-loading areas, and secondarycontainment basins. • Chlorine producers use flake-rein-forced linings for elevated tempera-ture brine storage tanks. • Municipal sanitation facilities usefiberglass- and flake-reinforced lin-ings and coatings for grit chambers,sumps, and wet wells. • Glass flake-reinforced polyesterlinings are used in food-related ap-plications such as starch tanks.

Application ConsiderationsEnvironmentTemperature of the surface and theadjacent air typically should be be-tween 45 and 120 F (7 and 49 C)during product application to pro-vide proper cure. Excessive temper-ature can cause bubbling, pinholing,or high thermal stress in the finishedlining. Consult the manufacturer’s lit-erature for the exact temperaturerange.

The surface temperature should beat least 5 F (3 C) above the dew

point of the air in the work area toavoid condensation or applicationon a wet surface.

Surface PreparationBecause of the generally high thick-ness of these systems and their useat elevated temperatures, proper sur-face preparation is essential to prod-uct performance.

Concrete surfaces should be abra-sive blasted and have sufficient ten-sile strength for the system being ap-plied. Minimum acceptable tensilestrength is about 200 to 300 psi (1.4to 2.1 MPa), which is the maximumtensile strength achieved by portlandcement concrete. Surface tensilestrength can be determined in accor-dance with ASTM D 4541, StandardTest Method for Pull-off Strength ofCoatings Using Portable AdhesionTesters.

Steel should be blasted with acoarse, angular abrasive to producea minimum profile of 3 mils (75 mi-crometers). Shot blasting produces apeened surface, so grit blasting is re-quired.

Stainless steel and alloys may re-quire harder or larger blast media orhigher blast pressures to achieve thedesired profile. Surface cleanlinessin accordance with SSPC-SP 5, WhiteMetal Blast Cleaning, is almost al-ways required.

Product ApplicationApplication procedures for thesethick-film lining systems includetroweling, rolling, and spraying. Ap-plicators should have special train-ing and experience with the methodbeing used, and they should closelyfollow the recommendations of thelining manufacturer for equipmentand procedures.

Components of the materialshould be mixed in strict accordancewith published procedures. Thick-ness and time between coats shouldbe within allowable limits.

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Quality ControlProceduresQuality control procedures shouldverify environmental conditions dur-ing surface preparation and applica-tion, proper mixing, applied thick-ness, and continuity of the lining.

Since lining thickness is importantto establish a barrier to chemical at-tack and permeation, it should be checked at pre-established spac-ing or locations to ensure that theminimum allowable thickness hasbeen applied.

Excessive thickness may detractfrom lining performance by causingcracking, so a maximum thickness isusually established. Dry film thick-ness is checked using various mag-netic gauges on steel substrates andeddy current gauges on other metal-lic substrates. Coating thickness onconcrete is checked with wet filmgauges during application.

Lining continuity—the absence of

holes through the lining—is impor-tant so that corrosive material doesnot have a path to attack the sub-strate. For these thick linings,the only practical method of inspec-tion is with a high voltage holidaydetector.

NACE RP 01-88, Standard Recom-mended Practice for Discontinuity(Holiday) Testing of Protective Coat-ings, presents the method for highvoltage spark testing. Consult thelining manufacturer for the maxi-mum voltage to use. Where a holein the lining exists, the high voltagewill cause a spark to jump throughto the substrate. Using too high avoltage may produce a holiday inthe film.

Steel substrates are, of course,very conductive. Concrete substratesusually require special conductiveprimers for reliable testing. Themethod recommended for testing on concrete surfaces is ASTM D

4787, Standard Practice for Continu-ity Verification of Liquid or SheetLinings Applied to Concrete Sub-strates.

Health and SafetyPrecautionsProcedures for protecting workers’safety and health are contained inthe lining manufacturers’ publishedinstallation instructions and MaterialSafety Data Sheets. Worker protec-tion procedures should be followedcarefully. Following are some gener-al comments about exposure levelsand the risks of styrene.

The American Conference of Gov-ernmental Industrial Hygienists hasdetermined that styrene monomerhas a threshold limit value (TLV) of 50 ppm as an eight-hour, time-weighted average (TWA). Areaswhere styrene is used should be well ventilated to avoid buildupof fumes.

Overexposure to styrene is report-ed to have adverse health effects onworkers. Proper skin protectionshould be worn, and appropriaterespiratory protection should beused, especially if styrene vapors ex-ceed 50 ppm. Among the observedeffects are skin irritations; eye, nose,and throat irritations; depression ofthe central nervous system; damageto the peripheral nervous system;and chromosomal changes. Al-though styrene has been classifiedas a possible human carcinogen,studies have not followed enoughworkers long enough to accuratelyassess the cancer risks of occupa-tional exposure.2

Uncured resins are flammable, sono welding or open flames shouldbe allowed in or near the work area.

ConclusionA wide range of polyester and vinylester lining products is being usedfor high performance, cost-effectiveprotection of steel and concrete sur-faces subject to chemical environ-





ments. Other advantages of thesesystems include their adhesion,strength, flexibility, solvent resis-tance, and heat resistance.

However, chemical resistance maybe reduced by the addition of fillersor reinforcements and by contactwith oxygen during cure. Also, theyusually perform better in acidic thanin alkaline environments. Particulatefiller or aggregate is added to somepolyester and vinyl ester lining sys-tems to extend the base resin.

In other cases, they are reinforcedwith various kinds of fiberglass or with glass or mica flakes. Thesethick-film lining systems typically are applied by trowel, roller, orspray equipment. Proper liningthickness is essential to provide ef-fective protection in a myriad of in-dustrial uses. JPCL

References1. Louis C. Sumbry, Robert Trull,

and Jacqueline Klaiss, “The Successful Application of FRPLinings in Above-Ground StorageTanks: A 20-Year History,” JPCL(March 1990), 40-44.

2. Carl Zenz, Ed., OccupationalMedicine, Third Edition (St.Louis, MO: Mosby, 1994), pp.724-729.

BibliographyASTM Committee D 33. Publication

STP 837, Manual of ProtectiveLinings for Flue Gas Desulfuriza-tion Systems. Philadelphia, PA:ASTM, 1984.

Barkey, T.D., W.R. Slama, and N.B.Fancher. “Physical and Mathe-matical Representations for the Determination of Crack-Bridging Ability of Lining Sys-tems.” In Managing Costs andRisks for Effective and DurableProtection: Proceedings from the SSPC 94 Seminars (SSPC 94-19). Atlanta, GA, November1994. Pittsburgh, PA: SSPC, 1994.

Nau, Patrick R., and Benjamin S.Fultz. “Coatings and Linings forSecondary Chemical Contain-ment in Power Plants.” JPCLOctober 1990: 42-49.

Severance, W.A. “Monolithic Liningsfor Chemical Waste Disposal.”Materials Performance August1981: 36-40.

Severance, W.A., and M.J. Galloway.

“Monolithic Linings for Immer-sion Service.” In Pulp and Paper Industry Corrosion Prob-lems . Houston, TX: NACE, 1974.

Washburn, Robert B., Marshall J.Galloway, and William R. Slama.“Reinforced, Chemical-Resistant,Thermoset Linings.” JPCL Octo-ber 1985: 30-42.

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