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Coating Types, Failure Modes, and Inspection Criteria 26-1Chapter 26: Coating Types, Failure Modes, and Inspection Criteria

Objectives

When this module is complete, you willhave knowledge and understanding of:

Curing mechanisms Solvent-evaporation (Non-convertible)

Coatings Polymerization-cured coatings

26.1 IntroductionEarlier chapters discussed various coatingsand their methods of curing. This chapterdeals with the unique problems coatinginspectors need to understand. Each curetype has unique inspection concerns inspec-tors need to understand to know what to lookfor and how and when to test the coating. Ifthe cure type is not on the product datasheet, inspectors should contact the coatingmanufacturers technical service depart-ment.

26.2 Curing MechanismsAs stated previously, there are two catego-ries of curing, each with several sub catego-ries. The two major curing mechanismcategories are: non-convertible (no chemi-cal change during the cure cycle) and con-vertible (some chemical change during thecure cycle).

26.3 Solvent-Evaporation Cure (Non-convertible) Coatings

Solvent-evaporation cured coatings simplyharden as the solvent evaporates. In coun-tries with active clean air programs solvent-evaporation cure materials are in limitedsupply since they contain a large amount ofsolvent that dissolve resins.

26.3.1 Chlorinated Rubber CoatingsThese single-package coatings were oncecommonly used in both the chemical processindustry and the marine industry because oftheir excellent petro-chemical, water, andUV resistance.

26.3.1.1 Failure ModesInspectors should ensure that existing chlori-nated rubber coatings should never be over-coated with a convertible coating such as anepoxy mastic during maintenance projects.

Figure 26.1 PinholesNACE International 2011 Coating Inspector Program Level 2July 2012

26-2 Coating Types, Failure Modes, and Inspection Cri-

Overcoat chlorinated rubber only with chlo- 26.3.2.1 Failure Modes

rinated rubber, a single package waterbornematerial, or possibly a solvent-free chemicalcured coating. To determine if the existingcoating is solvent sensitive (as most evapo-rative cure coatings are) simply rub the sur-face with a solvent soaked rag. If this affectsthe existing coating, it is safe to assume thatit should not be overcoated with a convert-ible coating. If a coating containing solventis applied to a hot surface, the coating willnot flow out and will leave an uneven sur-face with pinholes and low adhesion. Sol-vent entrapment can cause in-serviceblistering (Figure 26.1).

26.3.1.2 Inspection CriteriaDFT, surface temperature, and the overcoatwindow are all necessary inspection pointswith chlorinated rubber coatings. Follow theovercoat window and DFT recommended bythe manufacturer to avoid solvent entrap-ment. Also monitor the surface temperatureduring application to ensure it does notexceed the recommended maximum andcause too-rapid solvent evaporation.

26.3.2 Vinyl CoatingsVinyl coatings have the same issues as chlo-rinated rubber coatings. Vinyl coatings arecommonly used in water tanks and as inte-rior linings in water pipes. When used as alining they are applied in multiple coats withvery thin DFTs for each coat. Vinyl coatingscan have a solids content as low as 25%, sosafety is major concern when workingaround them. A big concern is also the largeamount of solvent that moves off into thesurrounding atmosphere.

Solvent blistering is a common form of fail-ure in vinyl coatings (Figure 26.2). This isusually caused by poor ventilation duringapplication, excessive DFT per coat, or fail-ure to follow the recommended recoat win-dow.

Figure 26.2 Blistering

26.3.2.2 Inspection CriteriaDFT, surface temperature, and the overcoatwindow are all necessary inspection pointswith vinyl coatings. Follow the overcoatwindow and the DFT recommended by themanufacturer to avoid solvent entrapment.Also monitor the surface temperature duringapplication to ensure it does not exceed therecommended maximum and cause a too-rapid solvent evaporation.

26.3.3 Acrylic CoatingsAcrylic resins are commonly blended withother resins because of their excellent resis-tance to UV degradation. Additionally, theyare used as the main, or singular resin, inwater-borne coatings with very low VOC.

26.3.3.1 Failure ModesWhen a single acrylic resin is the only resinin an acrylic coating, the most common fail-Coating Inspector Program Level 2 NACE International 2011July 2012

Coating Types, Failure Modes, and Inspection Criteria 26-3

ure modes are the failure to fully cure, and 26.3.4.2 Inspection Criteria

the failure to adhere when used as a primer.These failures are caused by either exceed-ing the recommended DFT or applying thematerial in hot and/or windy conditions. Ifthe co-solvent evaporates too quickly fromthe surface of the coating film, it traps sol-vent in the lower layers of the film andretards or stops the coalescence process.Applying the primer to a hot surface can pre-vent it from flowing out, which reducesadhesion (Figure 26.3).

Figure 26.3 Delamination from Substrate

26.3.3.2 Inspection CriteriaDFT, surface temperature, wind speed, andthe overcoat window are all necessaryinspection points with acrylic coatings.

26.3.4 Bituminous CoatingsBoth hot-melt and cold-applied bituminouscoatings are used in the pipe coating indus-try, and at times, for other industries aroundthe world. These coatings are normally shopapplied.

26.3.4.1 Failure ModesLong periods of sunlight exposure causeembrittlement of bituminous coatings andcracking (Figure 26.4) and delamination.Holidays are the most common problemwhen they are shop-applied.

The coating inspector needs to follow theinspection criteria for the particular productand the facility applying it. A close inspec-tion for holidays is necessary, paying careful

Figure 26.4 Cracking (Coating shown is not bituminous)

attention to the bottom side and the areaswhere the application equipment has diffi-culty reaching.

26.4 Polymerization-Cured Coatings

Temperature affects all coatings that curethrough a chemical reaction. This is a posi-tive heat-cured material, but this is generallya negative. There are a few single-packagematerials in this group, such as alkyds andmoisture cures, however most polymeriza-tion-cured coatings come in two or morecontainers that cannot be mixed until justprior to use. These two facts are also theleading cause of failure for polymerization-cured coatings.NACE International 2011 Coating Inspector Program Level 2July 2012


26.4.1 Oxygen-Induced 26.4.2.1 Epoxy Two-Component (Co-

Polymerization Coatings

26.4.1.1 AlkydsAlkyds absorb oxygen from the surroundingatmosphere and uses the 02 molecule toreact with the alkyd molecule in a processcalled oxidation.

26.4.1.1.1 Failure ModesThe most common problem with alkyds iswrinkling and/or a soft film caused fromapplying the coating too thickly. The topsurface cures and seals the lower levels ofthe film from the oxygen they need to cure.The other common issue is putting the coat-ing into service before it has time to fullycure.

26.4.1.1.2 Inspection CriteriaEnsure WFT readings are taken frequentlyby the applicator. Generally, any WFT over75 or 100 m (3 to 4 mils) in a single coat istoo thick. The inspector should also confirmthe applied material is cured before anothercoat is applied. Since oxygen-inducedpolymerization coatings normally have along cure time before they are ready for ser-vice, inspectors should make sure ownersknow not to package or use alkyd-coatedassemblies until the coating has reached itscure-to-handle stage.

26.4.2 Chemically Induced Polymerization Coatings

When two compounds are mixed together toform another compound, it is called chemi-cally-induced polymerization. Most of theindustrial and marine coatings in use todayare chemically-induced polymerization coat-ings.

Reactive) CoatingsEpoxy coatings are the most widely usedindustrial/marine coatings. They come in avariety of types, however the most commonfailure modes are similar across all types.

26.4.2.1.1 Failure ModesThe following failure modes and theircauses are usually apparent:

Failure to cure caused by improper mix-ing including a too short induction time, or temperatures above or below the rec-ommended maximum and minimum

Cracking caused by applying too thickly Pinholes caused by applying too thinly Sagging caused by applying too thickly,

over-thinning, or a too long pot life Delamination from previous coat caused

from exceeding the overcoat widow, coat-ing on a dirty surface, or applying over amine blush (Figure 26.6, Figure 26.7)

Chalking caused by UV (sunlight) expo-sure or other radiation (Figure 26.5)

Figure 26.5 ChalkingCoating Inspector Program Level 2 NACE International 2011July 2012


it. Use this to calculate the necessary induc-Figure 26.6 Amine Blush

Figure 26.7 Amine blush in removal process

26.4.2.1.2 Inspection CriteriaInspectors need to keep a careful watch onthe person mixing; this job is sometimes per-formed by the newest person on the team. Itis too easy to leave the cure component outof one can by mistake, particularly if themixer is inexperienced. Ensure mixing isdone correctly, using the correct equipment,for sufficient time for the type of coating,and for the size of the unit. Ensure the entirecure is poured from its container into thebase. The cure component is frequently athick material and may not pour easily.

In a fast-paced production job the mixer maynot allow the necessary induction time. Notethe time the material is mixed, and markeach can with the time the mixer came out of

tion time based on the materials tempera-ture. Mark the container with the time it canbe used.

Inspectors need to also watch the environ-mental conditions, especially the dew pointin the early hours of the day. For most epoxycoatings, moisture on the surface is a poten-tial cause of delamination. Cooler tempera-tures in the evenings retard an epoxys curetime. Check the temperatures during cure atleast every 4 hours. Some situations mayrequire using a data logger to track tempera-tures every few minutes during the curecycle. Only count the hours of cure when thesurface is at the curing temperature. Formost epoxy paints this temperature is above4.5C (40F).Because epoxies and epoxy blends workwell on a broad range of applications,inspectors need to know the exact surfacepreparation required for each project. Whenwhite metal is specified, the inspector mustensure the requirement is met. Specificationrequirements vary widely; sometimes alower level of cleaning is required, or some-times the specification requires epoxy to beapplied over damp, oil contaminated sur-faces, or underwater.

All epoxy coatings can be applied too thinly,and many can be applied too thickly withoutsagging. Inspectors must ensure the applica-tor uses a WFT gauge and follows the DFTreading standard specified, as well as checkDFT in hard to reach areas.

When using epoxies, each case is different,so the inspectors most difficult task isensuring the specified epoxy is used andNACE International 2011 Coating Inspector Program Level 2July 2012


applied following all the required steps and Ensure the surface is totally oil and contami-

conditions for the material and the project.

26.4.2.2 Zinc-Rich EpoxyThis epoxy coating has powdered zinc addedto it. It is supplied as either a two-compo-nent material with the zinc already in thebase, or as a three-component material withthe zinc to be added by the applicator at thetime of mixing.

26.4.2.2.1 Failure ModesFailure modes are the same as with a stan-dard epoxy. Use this material only as aprimer. If it is applied over another coating,it will not provide the advertised protectionto the surface.

26.4.2.2.2 Inspection CriteriaDue to the high load of zinc, zinc-rich epox-ies are more difficult to mix. Because of thisdifficulty, inspectors must know the propermix ratio and ensure all of the zinc suppliedin the kit is used. They must also verify thatthe pump is constantly agitated to keep thezinc in suspension.

As always, ensure all mixing and applicationcriteria in the specification are followed.

26.4.2.3 Polyester/Vinyl Ester Coatings

Polyester and vinyl ester coatings are used inspecial situations when a chemical or abra-sion-resistant coating is required. A highdegree of surface preparation is commonlyspecified.

26.4.2.3.1 Failure ModesFailure to cure is one of the most commonproblems. Hardness testing may be requiredto determine if the proper cure is achievedbefore returning the surface to service.

nant free, or blisters can form.

Because many of these products have glassfiber included with the resin (either mixed inor added during application), wicking can bea problem. Each glass fiber must be com-pletely wetted out to prevent moisture wick-ing into the film and the substrate. Wickingcauses underfilm corrosion, blistering and/ordelamination (Figure 26.8).

Figure 26.8 Blistering

26.4.2.3.2 Inspection CriteriaPerform all of the standard tests for theseproducts, and possibly a hardness test ifrequired.

26.4.2.4 Moisture-Cured UrethaneThese materials are used in areas of highhumidity where other materials generallycannot be used. They are frequently singlepackage materials but must be applied instrict accordance with the owners and man-ufacturers requirements.

26.4.2.4.1 Failure ModesMoisture-cured urethane is prone to failureto cure if used in areas of low humidity. Thiscoating must be able to absorb moisturefrom the surrounding atmosphere. Do notCoating Inspector Program Level 2 NACE International 2011July 2012


permit flooding with water. With a low 26.4.2.5.2 Inspection Criteria

humidity environment, the only proper treat-ment is to increase the local humidity bymisting the area.

Moisture-cured urethane will blister anddelaminate if applied to surfaces not cleanedin accordance with the specification.

26.4.2.4.2 Inspection CriteriaThis standard inspection technique requiresan extra careful watch on the humidity dur-ing the cure cycle.

26.4.2.5 Two-Component Thin Film Urethane Coatings

These products are most commonly used astopcoats over epoxies due to their good-to-excellent UV resistance and their wide avail-ability in different colors.

26.4.2.5.1 Failure ModesCommon failure modes include:

Delamination, often due to application afterthe overcoat window (Figure 26.9).

Color and gloss differences. These occur infinished film and are caused by using two ormore different batches of material, or fromusing two or more application techniques inadjoining areas. Changes in appearances arealso seen if the DFT is uneven across thesurface.

Blushing. This can be caused by moistureon the surface during the cure.

Failure to cure. This can happen if thinneradded during application contains any mois-ture. Please note that bulk thinners pur-chased at low cost may contain some levelof water.

Use the required standard inspection tech-niques and closely watch the DFT. Ensurethat if any thinner is used, the coating sup-plier approves in writing.

Figure 26.9 Cracking

26.4.2.6 Thick Film Polyurethane, Polyureas and Their Hybrids

These products are applied by heated pluralairless spray. They have a very short pot life,sometimes as short as 9 seconds. Althoughgrouped as a single family of materials, theindividual products often have very differentuse and application characteristics. Inspec-tors must understand how the specializedspray equipment works and understand theunique mixing at the tip of the gun.

26.4.2.6.1 Failure ModesDelamination. Delamination is caused byan improper specification. Polyureas arenormally applied over an epoxy primerwhen used on steel, but this is not requiredwhen applied over concrete. Polyurethanesand some polyurea hybrids are commonlyapplied directly to steel, but they sometimesrequire an epoxy primer on concrete.

Failure to cure. Generally caused by thefailure of the equipment to heat or pumpproper amounts of each material to the gun,NACE International 2011 Coating Inspector Program Level 2July 2012


or caused by the gun failing to spray both

sides in the proper ratio.

26.4.2.6.2 Inspection CriteriaFollow standard inspection techniques.

26.4.2.7 SiloxanesThese can come as single-package or two-component materials and are normallyblended with other resins such as acrylic,epoxy or polyurethane.

26.4.2.7.1 Failure ModesDelamination. One coat may delaminatefrom the previous coat; this is caused byapplication over a non-compatible product(Figure 26.10).

Cracking. This is usually caused by animproper formula, and delamination (Figure26.11).

Figure 26.10 Delamination

Figure 26.11 Cracking

26.4.2.7.2 Inspection CriteriaFollow standard inspection procedures. Inaddition, pay close attention to the filmthicknesses. Confirm that each product inthe system is applied in its proper order.Also, ensure that the products in the systemare compatible and meet the specifiedrequirements.

26.4.2.8 Silicone CoatingsThese high-temperature materials areapplied over IOZ or applied directly to steel.These materials require a two-step cure pro-cess. At first, they react like any solvent-evaporation material they harden within avery short time. However, they do not reacha fully cured state or adhere properly untilheated. In many cases, the heating is done inservice and increases incrementally over aset period of time.

26.4.2.8.1 Failure ModesDelamination. Generally due to animproper heat cure cycle (Figure 26.12).Coating Inspector Program Level 2 NACE International 2011July 2012


26.4.4 Water-Borne Inorganic Zinc Figure 26.12 Delamination

26.4.2.8.2 Inspection CriteriaCarefully read the specification and theproduct data sheet. Pay close attention torequirements to slowly and incrementallyraise the heat the first time these materialsare placed in service.

26.4.3 Solvent-Borne Inorganic Zinc Coatings

These coatings cure both by solvent evapo-ration, and a chemical reaction from absorb-ing moisture from the surroundingatmosphere. This may take several days tohappen, although it appears to cure withinminutes or seconds of application. These canbe used as preconstruction primers, but mustbe applied at only19 m (.75 mils).

26.4.3.1 Failure ModeFailure to cure. Caused by overcoating toosoon.

Mud cracking. Caused by an excessivelythick application typically over 125 m(5 mils).

26.4.3.2 Inspection CriteriaPay careful attention to the curing cycle ofthese materials. The inspector must ensurethey are fully cured prior to overcoating orpackaging.

CoatingsThese coatings cure by water evaporationand absorbing carbon dioxide from theatmosphere. The cure may take days, but thecoating appears to cure within minutes ofapplication. This has use as a pre-construc-tion primer if applied at 19 m (.75 mils).

26.4.4.1 Failure ModesFailure to cure. Caused by overcoating toosoon.

Mud cracking. This is caused by applyingan excessively thick coating, typically over125 m (5 mils).

26.4.4.2 Inspection CriteriaPay careful attention to the curing cycle ofthese materials. The inspector must ensurethey are fully cured prior to overcoating orpackaging.

26.4.5 Water-Borne CoatingsMany coatings use water as a thinner or dilu-ent. The major concern is preventing freez-ing during shipping and storage.

26.4.5.1 Failure ModesFailure to cure is caused by the water evap-orating too rapidly due to excessive heat onthe surface, or excessive air flow over thesurface.

26.4.5.2 Inspection CriteriaUse standard inspection criteria, paying par-ticular attention to surface temperatures ifhigh heat is expected, particularly to the topsof structures in full sunlight.NACE International 2011 Coating Inspector Program Level 2July 2012


26.5 Case Study Application of a water-borne acrylic finish

The exterior of a 20-year-old carbon steelground storage petroleum tank located in anarid desert climate was being blasted andcoated with a three-coat single packagewater-borne acrylic coating system. Afterairless spray application of the primer andintermediate coating on the top and 50% ofthe sides, the application contractor calledthe coating manufacturer and told them thematerial was not curing, ever after severaldays at 38C (100F) plus temperatures.26.6 DetailsThe specification called for:

Abrasive blast in accordance with NACE 3/SSPC SP10 Near White Blasting Clean-ing

Application of a water-borne acrylic primer at 75 to 125 m (3 to 5 mils)

Application of a water-borne acrylic inter-mediate coat at 100 to 150 m (4 to 6 mils)

coat at 50 to 75 m (2 to 3 mils)No inspection requirements were included inthe specification except the statement thatthe coating manufacturers recommends pro-cedures be followed and that the contractorfollow industry standard inspection proce-dures.

Application and cure times between coatsand final cure were the same for all threeproducts and were listed on their data sheetsas:

26.6.1 Application ConditionsReview Table 26.1 for application condi-tions.

26.6.2 Curing ScheduleThese times are based on a 50-75 m (2.0-3.0 mils) DFT. Higher film thickness, insuf-ficient ventilation, high humidity, or coolertemperatures will require longer cure times(Table 26.2).

Table 26.1: Application Conditions

Condition Material Surface Ambient Temperature Humidity

Normal 16-32C (60-90F)18-29C (65-85F)

18-32C (65-90F) 10-80%

Minimum 10C (50F)50F (10C)

10C (50F) 0%

Maximum 40C (105F)54C (130F)

43C (110F) 85%Coating Inspector Program Level 2 NACE International 2011July 2012


Table 26.2: Curing Schedule The material temperature was not taken or A note on the data sheets stated: Dry FilmThickness 50-75 m (2.0-3.0 mils); do notexceed 75 m (3.0 mils) in a single coat.

26.7 Pertinent NotesWhen the manufacturers technical serviceperson arrived on site, he first reviewed thecontractors and inspectors notes of theproject.

26.7.1 Contractors Notes The start of the project coincided with the

beginning of the summer season. The owner did not have a coating inspec-

tor on the project and relied on the con-tractor who provided a part time non-certified coating inspector.

This was a single shift job and all work took place between 7 a.m. and 5 p.m. each day.

Environmental conditions, including: ambient and surface temperature, dew point and %RH, were taken and recorded at the beginning of the day about 8 a.m., around noon, and at the end of the work-day about 5 p.m. On some days, the noon and end of shift readings were not recorded.

On some days no environmental readings were recorded.

Wind speed was not recorded and the inspector did not have a wind velocity meter.

recorded. There was a verbal comment from the

inspector to the manufacturers technical service person that since this was the des-ert, every day was just the same as the previous day as far as the weather went. He also proudly commented that they had to stop painting and hold off until the next morning on several occasions, since the wind was blowing so hard in the after-noon that the man-lifts they worked out of started to swing too much.

The abrasive blasting was performed with silica sand and was accepted by the coat-ing inspector as being compliant with the specification. There were no photographs or any recorded test results such as the ISO 8503-3 Dust Tape test to verify his claim. When asked if he had a copy of SSPC Vis-1 he said he did not.

No testing for soluble contaminants was required by the specification or performed by the contractor.

Blasting was performed from the begin-ning of the shift until about 3 p.m. when the blasted area was blown down and coated with the primer.

There were no records of WFT being taken. When questioned about it the paint-ing supervisor said that all of his painters checked WFT constantly while applying the coating, but they did not record.

The material was thinned with clean water, but no record of the amount of thin-ner was kept. The painting supervisor claimed they followed the manufacturers data sheet exactly. There was no evidence of any liquid measuring devices at the job site.

26.7.2 Inspectors Daily LogThe project had been in progress for 7 dayswhen the coating manufacturers technicalservice person showed up. The daily notes

Surface Temp and 50% RH

Dry to Handle

Dry to Topcoat

10C (50F) 3 hours 3 hours

24C (75F) 2 hours 2 hours

32C (90F) 1 hour 1 hourNACE International 2011 Coating Inspector Program Level 2July 2012


recorded by the contractors inspector were (99F), RH 15%, tank surface on roof 40C

as follows:

26.7.2.1 Day One and TwoMoved on job, brought in equipment, paint,and grit, and covered with tarp.

Bright sun, no rain in forecast.

Ambient temperature was 32C (90F) inthe morning, and 43C (110F) at 5 p.m.when leaving the job site. Did not have toolto measure RH but was really hot and dryfeeling; must have been pretty low humidity.Sure a lot of sand blowing around in theafternoon!

26.7.2.2 Day ThreeSet up and started to blast on roof of tank,three blasters on roof starting in the middleand working out.

Ambient temperature was 32C (90F) at 8a.m., clear and sunny.

Ambient temperature was 36C (97F) at 12noon, still clear and sunny, wind starting topick up.

Ambient temperature was 43C (110F) at 4p.m., sunny but with a dust cloud from thewind, too windy to paint.

26.7.2.3 Day FourChecked blasting from previous day, stilllooked good, will complete blasting andprime the roof today.

Ambient temperature was 32C (90F) at7:30 a.m., clear and sunny.

Noon: Blasting on roof completed, looksgood, painters setting up. Air temp 37C

(105F).

1 p.m. wind picked up too much to paint,tarps blowing off stored materials.

2 p.m. put away materials and left jobsite.

26.7.2.4 Day FiveInspector not available due to a differentproject today. Supervisor reported thateverything went well, all temperatures weregood to go and the roof was painted with theprimer, and two drops were made on the sideby the blasters.

26.7.2.5 Day Six9 a.m. arrived at job site, blasting on sides.

Ambient temperature was 32C (90F) at 9a.m., clear and sunny, RH 12%.

Ambient temperature was 36C (97F) at 12noon, still clear and sunny, RH 12%.

Ambient temperature was 43C (110F) at 4p.m., clear and sunny.

Checked DFT of primer on roof and sides,took 25 or 30 readings on roof and another10 or 15 on the sides, average was 100 m(4 mils).

Primer on roof still a little soft, but notsticky. Gave approval to apply intermediatecoat based on the fact the primer had beenon for two days and must be cured by now.Told painters to wear booties so they wouldnot get the primer dirty. They used the blasthoses to blow down the roof before sprayingon the next coat.Coating Inspector Program Level 2 NACE International 2011July 2012


3 p.m. Blasting on sides completed with they said they would send someone out that

all areas blown down, looks like a good nearwhite blast, only a very few spots of paintvisible on the surface, really clean looking.

3:30 p.m. Intermediate coat being appliedto roof and portion of the sides. Primer beingapplied to bare steel portion of the sides andthe ladder.

5 p.m. One of the painters had to comedown off the roof since he burned his handwhen he touched the steel with his barehand. It did not seem bad enough to sendhim to the hospital so we had him soak it incold water. I guess I should check that tem-perature up there, but access is limited.

6 p.m. todays painting completed, looksgood!

26.7.2.6 Day SevenAmbient temperature was 32C (90F) at 9a.m., clear and sunny, RH 12%.

Ambient temperature was 36C (97F) at 12noon, still clear and sunny, RH 12%.

Ambient temperature was 43C (110F) at 4p.m., clear and sunny.

7 a.m. Material on roof still soft to thetouch, but not sticky. Soft on the sides also,except on the north side of the tank where ithas gotten hard like I think it should be.Checked the batch numbers on the paint andthere were several different numbers foreach product. Must be we got some badpaint!

Stopped the job and called the coating man-ufacturers technical service department;

afternoon.

26.8 Coating Manufactures Results

The manufacturers representative con-firmed that the coating was still fingernailsoft. He measured several places for DFTand found a film thickness (used plasticshim to measure through and subtractedshim DFT) ranging from 50 to 200 m (2 to8 mils) of primer and where the primer hadbeen overcoated the DFT was 75 to 400 m(3 to 16 mils). The surface temperature ofthe roof was 60C (140F) at 3 p.m. and thewind speed was 24 knots.

26.8.1 QuestionsYour team represents the coating manufac-turer. Answer the following questions:

1. List three things the inspector did wrong or neglected to do that should been have done.

2. List three things the owners specifica-tion writer could have done to improve the specification.

3. What could the application contractor have done to improve the quality of the job?

4. Why does your team think the coating was still soft to the touch on most of the tank and hard on the north-facing wall of the tank? What do you think can be done to fix it?NACE International 2011 Coating Inspector Program Level 2July 2012


Study Guide1. What are the two categories of curing and their definitions? ______________________________________________________________________

______________________________________________________________________ ______________________________________________________________________

______________________________________________________________________

2. List some examples of non-convertible coatings. ____________________________ ____________________________ ____________________________ ____________________________

3. What is a polymerization-cured coating? ________________________________________________________________________

4. List some examples of convertible-cured coatings. ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________

5. What is the cause of chalking in an epoxy coating? ________________________________________________________________________________________________________________________________________________

6. When using a solvent-borne inorganic zinc, what would be one common reasons for a fail-ure to cure? ________________________________________________________________________________________________________________________________________________Coating Inspector Program Level 2 NACE International 2011July 2012

Chapter 26: Coating Types, Failure Modes, and Inspection Criteria26.1 Introduction26.2 Curing Mechanisms26.3 Solvent-Evaporation Cure (Non-convertible) Coatings26.3.1 Chlorinated Rubber Coatings26.3.1.1 Failure ModesFigure 26.1 Pinholes

26.3.1.2 Inspection Criteria

26.3.2 Vinyl Coatings26.3.2.1 Failure ModesFigure 26.2 Blistering


26.3.3 Acrylic Coatings26.3.3.1 Failure ModesFigure 26.3 Delamination from Substrate


26.3.4 Bituminous Coatings26.3.4.1 Failure Modes26.3.4.2 Inspection CriteriaFigure 26.4 Cracking (Coating shown is not bituminous)

26.4 Polymerization-Cured Coatings26.4.1 Oxygen-Induced Polymerization Coatings26.4.1.1 Alkyds26.4.1.1.1 Failure Modes26.4.1.1.2 Inspection Criteria

26.4.2 Chemically Induced Polymerization Coatings26.4.2.1 Epoxy Two-Component (Co- Reactive) Coatings26.4.2.1.1 Failure ModesFigure 26.5 ChalkingFigure 26.6 Amine BlushFigure 26.7 Amine blush in removal process

26.4.2.1.2 Inspection Criteria

26.4.2.2 Zinc-Rich Epoxy26.4.2.2.1 Failure Modes26.4.2.2.2 Inspection Criteria

26.4.2.3 Polyester/Vinyl Ester Coatings26.4.2.3.1 Failure ModesFigure 26.8 Blistering


26.4.2.4 Moisture-Cured Urethane26.4.2.4.1 Failure Modes26.4.2.4.2 Inspection Criteria

26.4.2.5 Two-Component Thin Film Urethane Coatings26.4.2.5.1 Failure Modes26.4.2.5.2 Inspection CriteriaFigure 26.9 Cracking

26.4.2.6 Thick Film Polyurethane, Polyureas and Their Hybrids26.4.2.6.1 Failure Modes26.4.2.6.2 Inspection Criteria

26.4.2.7 Siloxanes26.4.2.7.1 Failure ModesFigure 26.10 DelaminationFigure 26.11 Cracking


26.4.2.8 Silicone Coatings26.4.2.8.1 Failure ModesFigure 26.12 Delamination


26.4.3 Solvent-Borne Inorganic Zinc Coatings26.4.3.1 Failure Mode26.4.3.2 Inspection Criteria

26.4.4 Water-Borne Inorganic Zinc Coatings26.4.4.1 Failure Modes26.4.4.2 Inspection Criteria

26.4.5 Water-Borne Coatings26.4.5.1 Failure Modes26.4.5.2 Inspection Criteria

26.5 Case Study26.6 Details26.6.1 Application Conditions26.6.2 Curing Schedule

Table 26.1: Application ConditionsTable 26.2: Curing Schedule26.7 Pertinent Notes26.7.1 Contractors Notes26.7.2 Inspectors Daily Log26.7.2.1 Day One and Two26.7.2.2 Day Three26.7.2.3 Day Four26.7.2.4 Day Five26.7.2.5 Day Six26.7.2.6 Day Seven

26.8 Coating Manufactures Results26.8.1 Questions1. List three things the inspector did wrong or neglected to do that should been have done.2. List three things the owners specification writer could have done to improve the specification.3. What could the application contractor have done to improve the quality of the job?4. Why does your team think the coating was still soft to the touch on most of the tank and hard on the north-facing wall of the tank? What do you think can be done to fix it?1. What are the two categories of curing and their definitions?2. List some examples of non-convertible coatings.3. What is a polymerization-cured coating? ________________________________________________________________________4. List some examples of convertible-cured coatings.5. What is the cause of chalking in an epoxy coating? ________________________________________________________________________ ________________________________________________________________________6. When using a solvent-borne inorganic zinc, what would be one common reasons for a failure to cure? ________________________________________________________________________ ________________________________________________________________________

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