Epoxy CoatingsGuide

A complete guide ofepoxy coatings for

industrial and marine

applications.

Epoxy coatings are generally packaged in two parts that are mixed prior to application. The two parts

consist of 1) an epoxy resin which is cross-linked with 2) a co-reactant or hardener. Epoxy coatings are

formulated based upon the performance requirements for the end product. When properly catalyzed and

applied, epoxies produce a hard, chemical and solvent resistant finish. They are typically used on concrete

and steel to give resistance to water, alkali and acids.

It is the specific selection and combination of the epoxy component and the hardener component that

determines the final characteristics and suitability of the epoxy coating for a given environment.

Epoxy ResinsFeatures

ChemicalCommon Types

Bisphenol A

Bisphenol F

Phenolic Novolac

Viscosity

Moderate – High

Moderate

Moderate – High

Flexibility

Moderate

Low– Moderate

Low

Resistance

Moderate

Moderate

High

Co-Reactant or HardenersTypes: Polyamide, Aromatic Amine, Amidoamine, Aliphatic Amine, Cycloaliphatic Amine, Aliphatic Amine Adduct

Features [co-reactants and hardeners rated top to bottom from best suited to least suited ]

FilmChemical Resistance

Flexibility

Best

Polyamide

Amidoamine

Phenalkamine

Cycloaliphatic Amine

Aromatic Amine

Aliphatic Amine Adducts

Aliphatic Amine

BlushResistance

Best

Polyamide

Phenalkamine

Amidoamine

Cycloaliphatic Amine

Aromatic Amine

Aliphatic Amine Adducts

Aliphatic Amine

Adhesion

Best

Polyamide

Phenalkamine

Amidoamine

Cycloaliphatic Amine

Aliphatic Amine

Aliphatic Amine Adducts

Aromatic Amine

ColorStability

Best

Polyamide

Amidoamine

Cycloaliphatic Amine

Aliphatic Amine Adducts

Aliphatic Amine

Phenalkamine

Aromatic Amine

Acids

Best

Aromatic Amine

Cycloaliphatic Amine

Aliphatic Amine

Aliphatic Amine Adducts

Amidoamine

Phenalkamine

Polyamide

Lo Temp.Application

Best

Phenalkamine

Aliphatic Amine

Aliphatic Amine Adducts

Cycloaliphatic Amine

Polyamide

Amidoamine

Aromatic Amine

Solvents

Best

Aliphatic Amine

Aliphatic Amine Adducts

Cycloaliphatic Amine

Aromatic Amine

Polyamide

Phenalkamine

Amidoamine

CorrosionResistance

Best

Polyamide

Amidoamine

Phenalkamine

Cycloaliphatic Amine

Aliphatic Amine Adducts

Aromatic Amine

Aliphatic Amine

Water

Best

Polyamide

Phenalkamine

Amidoamine

Cycloaliphatic Amine

Aromatic Amine

Aliphatic Amine

Aliphatic Amine Adducts

Viscosity

Best

Cycloaliphatic Amine

Aliphatic Amine

Amidoamine

Aromatic Amine

Aliphatic Amine Adducts

Phenalkamine

Polyamide

A lower gloss than expected

Areas rich in polyamide or amine content may exhibit

Common Causes for Irregularities and Finish Defects

Polyamide/Amine Blushor Surface EnrichmentOccurs when the proper cure cycle of catalyzed epoxiesis interrupted or slowed. The “lighter” polyamide or aminehardener separates from the epoxy and floats to the surfacewhere it oxidizes and turns yellow or brownish in color.

Check By:The polyamide/amine blush can be confirmed by rubbing thesurface lightly with a clean rag saturated with MEK or ReducerR7K54. The yellow appearance will be removed, but maylater return.

Caused By:

Improper Mixing·

yellowing/blushing and/or an oily exudate· Areas rich in epoxy content will appear normal in color

for a period of time, but may eventually discolor· May result in color variations along the same coated surface· Drying and curing times may be affected

Improper HardenerEpoxy coatings are formulated with optimum levels of ahardener for a given level of epoxy resin. This ratio differsfrom product to product. The use of an improper hardenermay result in an undercatalyzed or overcatalyzed product.

Improperly inducted epoxies will exhibit:·

· Yellowing becoming progressively worse over time· Polyamide/amine blushing· Poor color acceptance· Reduced chemical resistance· Softer film· Color float and/or color variation

It is possible that the coating material applied initially maydevelop low gloss and discolor, while the rest of the surface,painted with the same material, will appear normal asinduction time has increased.

Low TemperatureMost epoxies are formulated for application at temperaturesabove 50–55ºF. Temperatures below 50ºF will stop therate of the chemical reaction between the epoxy and thehardener. The evaporation of the solvents in the coatingare also inhibited.· Both of these conditions will increase the likelihood of

blushing, discoloration and down-glossing.· Be aware that surface temperatures may be much lower

than the air temperature. Epoxy coatings should never beapplied below the recommended temperature range, orwhen temperatures are expected to fall below the minimumrecommended temperature during the first 72 hours of cure.

High Humidity, Moisture Condensation, Stagnant Air

Undercatalyzed Films: · Most epoxies are designed for application up to a· May appear dry but will not fully cure· May appear soft and gummyOvercatalyzed Films:· May be hard and brittle· Both will result in discoloration, yellowing,

and reduced performance properties

Insufficient Induction (Sweat -In Time)Many epoxy coatings require a specified induction timein order to fully “compatibilize” the epoxy resin and thehardener. When required, this pre-reaction will reducethe likelihood of poor film appearance and poor coatingperformance. Lower temperatures and/or high humiditywill generally require longer induction periods.

maximum 85% RH· High humidity and/or the presence of moisture may

cause discoloration or a “greasy” feel and poor uniformityof appearance

· The polyamide/amine may separate and causediscoloration. Maximum effort should be made toincrease fresh air circulation to minimize this effect.

Insufficient Curing of

Water-Based Primers or FillersIf water-based primers are not sufficiently cured prior totopcoating, moisture migrating through the fresh epoxy filmwill inhibit the drying and curing of the epoxy. This will causediscoloration, low gloss and possibly delamination.

Common Causes for Irregularities and Finish Defects

Discoloration from ExposureUV Light (Sunlight)

Discoloration fromChemical Exposure

·

·

This is a surface phenomenon attributed to the naturaldarkening of epoxy resin upon exposure to UV or sunlight.This problem occurs most often in areas with intermittentsunlight, creating a “checkerboard” effect.The discoloration may be confirmed by scraping away thesurface layer with a knife to expose the underlying film whichwill appear lighter in color.

·

·

Certain chemical compounds, such as carbon monoxideand carbon dioxide, are known to react with freshly appliedepoxy films and cause discoloration. This discoloration willbe more pronounced in areas of high film build and in areaswith little or no air circulation.Check area for cleaning agents that may contain thesecompounds. Animal kennels or shelters are also suspectbecause of waste byproducts.

Epoxy Finishes: Resistance to YellowingProduct [epoxies rated top to bottom from best resistance to least resistance ]

Polysiloxane XLE-80 Best Resistance

Fast Clad DTM Waterbased Epoxy

Pro Industrial Hi-Bild Waterbased Epoxy

Water-Based Catalyzed Epoxy

Tile-Clad HS Epoxy

Water-Based Tile-Clad

Pro Industrial High Performance Epoxy

Epolon II Multi-Mil Epoxy

Macropoxy HS Epoxy

Macropoxy 646 Fast Cure Epoxy

High Solids Catalyzed Epoxy

Macropoxy 846 Winter Grade Epoxy

Sher-Glass FF

Tank Clad HS Epoxy

Dura-Plate MT

Least Resistance Dura-Plate 235

Common ProblemsDiscoloration/Yellowing··············Color Variation················Blushing·········Uneven

Gloss···············Exotherm (Hot Paint)····Poor Intercoat Adhesion···············Soft Film·············Tacky Film/Slow

Dry············Lifting/Wrinkling··········Bleeding······Pinholing·······Cratering········Low Film

Thickness···Sagging···········Cracking/Crazing·····Alligatoring···· Wro

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Key Issues to Consider During Selection and Use of Epoxies

Substrate Types: Steel, Concrete, etc. Is it suitablefor the coating and the environmental exposure?

Surface Prep Are the requirements adequate?

Temperature/Variations Normally above 55ºF for thefirst 72 hours of drying, and at least 5ºF above the dew point.

Humidity Normally below 85% required.

Environmental Exposure Is the coating suitablefor the conditions it will be exposed to?

Performance Requirements What performancecharacteristics will the coating be exposed to?(i.e. abrasion, flexibility, heat resistance, etc.)

Recoatability Will it be required and withinwhat time frame?

Application Methods Is the coating designed for the

Cost/Value Considerations Cost per milper square foot per year of life expectancy.

Film Build Is the coating able to comply withthe specifications?

Air Movement It is very important to have freshair circulating over the surface during drying.

Induction Time Critical, especially during coldweather and high humidity.

Pot Life Do not exceed. Coating may appearusable but will exhibit poor performance.

Aesthetics Be aware that some epoxies yellow morethan others. More noticeable in whites and off-whites.

Odor Will odor be a concern in or around the applicationarea? Solvent based, water-based, high solids epoxies.

specific method? (i.e. spray, brush, roll, squeegee/trowel)

Epoxies—Common Problems and Most Probable Causes

Epoxy Coating Comparison Chart

AmineEpoxies

PolyamideEpoxies

AmidoamineEpoxies

EpoxyPhenolics/Novolacs

Description Form very hard, adherentfilms with excellent chemicaland corrosion resistance.Amine cured epoxies areoften used as protectivecoatings and linings inhighly corrosive environ-ments. Amine epoxiesrequire care in handlingsince the amines can bemoderately irritating to theskin, and may causeallergic reactions.

Polyamide epoxiesgenerally offer the widestlatitude in coatingformulation. They areconsidered more resilientand flexible, and have betterweathering resistance and alongerpot life than amine curedepoxies. Polyamide epoxiesgenerally have less solventand acid resistance thanamine cured epoxies.

Amidoamines are reactionproducts of a polyamineand a fatty acid. Theirproperties generally fallbetween those of aminesand polyamides. They havegood water and corrosionresistance like amines,and good toughness likepolyamides. They haverelatively small molecularsize giving them low visc-osities and making them

These coatings allow widerange formulating latitude.Novolac epoxy resinincreases chemicalresistance and solventresistance. Increasing thelevel of phenolic increasesthe chemical and solventresistance, but the coatingloses flexibility. Somephenolics require heatcuring.

very good surface wetters.

Advantages · Excellent alkali and · Very good alkali and · Excellent surface wetting · High heat resistancewater resistance water resistance · Excellent adhesion · Excellent chemical

· Very good acid resistance· Excellent solvent resistance· Hard, abrasion

resistant film· Excellent corrosion

resistance· Excellent wettingof substrate

· Chemical/moisture barrier

· Good acid resistance· Longer pot life than amines· Easy to apply· Cures more quickly

than amines· Good weathering

characteristics· Good film flexibility· Excellent adhesion

· Excellent water resistance· Low viscosity· Longer pot lifethan amines

· Good gloss retention

resistance· Excellent solvent

resistance· Excellent corrosion

resistance· Hard, abrasion

resistant film

Disadvantages/Limitations

· Amines can beirritating/toxic

·

·

Faster dry than aminesChalks

·

·

Slow cureFair color retention

· Some may requireheat cure

· Relatively short recoat time· Relatively short pot life· Slower dry than

· High viscosity· Temperature dependent· Slow cure

· Temperature dependent · Relatively slow air cure· Chalks/may discolor· Relatively brittle

normal polyamides· Chalks/may discolor

Primary UsesRefer to product

-34·

· Severe chemicalresistant coating

·

·

Water immersionGeneral industrial

·

·

Barrier coatingSurface tolerant coating

· Severe chemicalresistance

data sheets forspecific useinformation

· Barrier coating· Offshore structures· Storage tanks,

structural steel· Bridges, power plants· Tank linings

· Offshore structures· Storage tanks,structural steel

· Water/wastewater plants· Tank linings· Bridges, power plants

· Where chemical andmoisture resistanceis required

· General industrial· Refineries· Bridges, power plants

· Tank linings· Secondary containment· General industrial· Refineries· Bridges, power plants

· Secondary containment · Secondary containment

S-W Products AminesShelcote II EpoxyShelcote II Flake FilledDura-Plate UHS

Kem Cati-Coat HSFiller/Sealer

Tile-Clad High SolidsRecoatable Epoxy Primer

Epoxy Mastic Aluminum II Phenicon HS EpoxyPhenicon Flake FilledEpo-PhenNova-Plate UHS

Tank Clad HS EpoxySher-Glass FF

KetiminesDura-Plate MTMacropoxy 920 PrePrime

PhenalkaminesDura-Plate 235

Water-BasedWater-Based Tile-CladZinc Clad VIFast Clad DTMWaterbased Epoxy

Copoxy Shop PrimerZinc Clad IVZinc Clad III HSHi-Solids Catalyzed EpoxyMacropoxy 646 Fast CureMacropoxy 846Winter Grade

Epolon II PrimerEpolon II Multi-MilMacropoxy HS EpoxyPro Industrial HighPerformance Epoxy

Epoxy Coating Comparison Chart

SiloxaneEpoxies

Coal TarEpoxies

Water-BasedEpoxies

EpoxyEsters

Description Siloxane epoxies are rela-tively fast curing coatingswith excellent stain andmar resistance. They haveexcellent color and glossstability. Siloxane epoxiesare typically used in highperformance industrialapplications. Also accept-able for architecturalapplications.

Coal tar epoxies are acombination of a basicepoxy resin and coal tar.The coal tar is in the formof a semi-liquid pitch andblended with the epoxyresin. The curing agentsfor coal tar epoxies areusually either amines orpolyamides. Coal tarepoxies offer excellent

Generally consist of anon-yellowing acrylic resindisbursed in water mixedwith an emulsified epoxyresin. They are relativelyhard, durable coatingswith moderate chemicalresistance. They offer goodstain resistance, abrasionresistance and resistance tomost commercial cleaning

A combination of epoxyresin and alkyd resinresulting in an air-dryingcoating. Epoxy estersprovide a hard, durable filmideal as a machinery finish.Recommended for generalatmospheric use in areasnot considered severelycorrosive.

resistance to fresh andsalt water and are highlyresistant to cathodicdisbondment.

agents and sanitizers. Theycan be used over previouslyapplied conventional paintsto upgrade the surface forbetter performance withoutwrinkling, lifting or bleeding.

Advantages · Very good weathering · High film build · Good chemical and · Hard, durable filmresistance with one coat solvent resistance · Easy to apply

· Hard, abrasionresistant film

· Very good acid resistance· Excellent color and gloss

retention· Relatively fast dry

· Excellent salt waterresistance

· Excellent water resistance· Excellent resistance to

cathodic disbondment· Economical

· Hard, abrasionresistant film

· Upgrades conventionalsystems to highperformance

· Water clean-up, low-odor· No strong solvents· Good adhesion· Very long pot-life· Good weathering

· One component· Good moisture

resistance· Minimal surfacepreparation

· Moderate cost· Low temperatureapplication

· Increased alkaliresistance over alkyds

Disadvantages/Limitations

·

·

Solvent resistantHeat resistant

· Not for potable water· Black color· Critical recoat time/

· Flash rusting on ferrousmetal unless primed

·

·

Fair solvent resistancePoor weatheringcharacteristics

difficult to recoat· Fair solvent resistance· Chalks/browns

· Poor exterior glossretention

Primary Uses · Bridges · Liner for sewage · Light/moderate · Moisture resistance· Refer to product

data sheets forspecific useinformation

· Marine· High performancefinish coating

· Kennels,

treatment tanks· Not-potable water tanks· Pipe coating· Penstocks, dam gates

industrial areas· Tile-like wall coating· Schools· Hospitals

· Where odor or lowtemperature limitationsprevent solvent-basedepoxy use

· Schools, jails, hospitals· High moisture areas· Stain resistant coating

· Offshore rigs· Paper mills· Chemical Plants· Secondary containment

· Food plants· Office areas· Kitchens· Hallways

· Abrasion resistance

· Nursing homes

S-W Products Polysiloxane XLE-80 Hi-Mil Sher-Tar EpoxyTar-Guard Coal Tar Epoxy

Water-Based Epoxy PrimerWater-Based EpoxyPro Industrial Hi-BildWaterbased Epoxy

To learn more, visit us atwww.sherwin-williams.com/im

or call 1-800-524-5979 to have

a representative contact you.

©2008 The Sherwin-Williams CompanyIndustrial & Marine Coatings2004096

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