3/31/2017 4.

CoatingDefects:MPIGroup

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Contents Translate
Contentslist 41
SamplePages Abrasion 44
AdhesionFailure 46
Authors Alligatoring 410
AlluminiumCorrosion 412
Contributors
ApplicationDefects 414
Translation Bittiness 418
Bleaching 419 ClickheretoorderFitz
1.Contents
Bleeding 420 Atlas2
2.WeldingFaults BlisteringGeneral 421
3.SurfaceConditions Blisteringintercoat 424
BlisteringNonOsmotic 426
4.CoatingDefects
BlisteringOsmotic 428
5.Microscopy Bloom 431
6.MarineFouling Bodying 432
Bridging 433
IndustryVacancies SubscribetoDrydock
BrushMarks 435
magazine
BubblesorBubbling 436
CargoDamage 437
CathodicDisbonding 440
Chalking 442
Checking 444
Cheesiness 447
ChemicalExposure 449
Cissing 451 SubscribetoPCE
Cobwebbing 453 magazine
Cracking 454
CrackingatWelds 458
Cratering 460
Crazing 461
Crowsfooting 463
Degradation 465
Delamination 466
Dryspray 469
EdgeCorrosion 471
Efflorescence 473
Erosion 475
Exudation 477
Fading 478
FatEdge 479
FeatherEdging 480
Filiform(Corrosion) 482
FishEyes 483
Flaking 4.84
Flocculation 4.87
Flooding 488
Flotation 489
Galvanising(Lossofadhesionofcoating) 490
Grinning 492
GritInclusions 4.93

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Growth 495
HeatDamage 497
ImpactDamage 499
IncorrectCoatingSystem 4101
IncorrectCoatingThickness 4103
IntercoatContamination 4104
Knotting 4105
LaminationsorShelling 4106
MechanicalDamage 4108
Milkiness 4110
Millscale 4111
Misses/Skips/Holidays 4113
MissingTopcoat 4115
MudCracking 4116
OrangePeel 4117
Overspray 4119
Peeling 4121
Pinholes 4123
PrimerDegradation 4125
RainDamage 4127
RippledCoating 4129
Root(Wood) 4130
Runs 4132
RustJacking 4133
RustRashing(ThermalSpray) 4134
RustRashing 4135
RustSpotting 4137
RustStaining 4140
Sags 4142
Salts 4146
Saponification 4147
Settlement 4148
Skinning 4149
SolventLifting 4150
SolventPopping 4151
Staining 4152
StressCracking 4154
StripeCoats 4157
Tackiness 4159
UnderCuredCoating 4160
Undercutting 4161
WaterSpotting 4163
Wrinkling 4164
ZincSalts 4167

Abrasion
Description:Themechanicalactionofrubbing,scraping,scratching,gougingorerosion.

ProbableCauses:Removalofaportionofthesurfaceofthecoatingorinseverecasesremovalto
exposethesubstratebycontactwithanotherobjectsuchastheuseofmetalchainsforlifting,
cargo,fenders,orthegroundingofaship.

Prevention:Useofabrasionresistantcoatingsformulatedwithparticularregardtoresinsand
extenderpigments.Withseverecasesofabrasiontheeffectswillonlybereducedorlimitedbyan
abrasionresistantcoating.

Comment:Dependsontheextentofthedamageandcouldrangefromindividualareasprepared
bymechanicalcleaningtotheblastcleaningoflargeareas.Applicationofanabrasionresistant
coating.

AdhesionFailure
Description:Paintfailstoadheretosubstrateorunderlyingcoatsofpaint..

ProbableCauses:Surfacecontaminationorcondensation,incompatibilitybetweencoating
systemsandexceedingtheovercoatingtime.

Prevention:Ensurethatthesurfaceisclean,dryandfreefromanycontaminationandthatthe
surfacehasbeensuitablyprepared.Usethecorrectcoatingspecificationandfollowtheadvised
overcoatingtimes.

Repair:Dependsupontheextentofadhesionfailure.Removalofdefectiveareaswillbe
necessarypriortoadequatepreparationandapplicationofcorrectcoatingsystemto

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manufacturersrecommendations.

Alligatoring
(alsoknownasCrocodiling)
Description:Verylarge(macro)crazing/crackingwhichresemblestheskinofanalligatoror
crocodile.Cracksmaypenetratethroughtotheundercoatordowntothesubstrate.

ProbableCauses:Internalstressesinthecoatingwherethesurfaceshrinksfasterthanthebody
ofthepaintfilm.Excessivefilmthicknessandlimitedpaintflexibility.Applicationofahardtopcoat
overamoreflexiblesofterundercoat.Applicationoftopcoatbeforetheundercoathasdried.

Prevention:Usecorrectcoatingspecificationandcompatiblematerials.Avoidexcessivefilm
thickness.Avoidapplicationathighambienttemperatures.

Repair:Repairwilldependuponsizeandextentofalligatoring.Abradeorremoveallaffected
coatsandapplysuitableundercoatandtopcoat.Followrecommendedapplicationprocedures

AluminiumCorrosion
Description:Blisteringand/orlifting/disruptionofthepaintcoatingduetotheformationof
aluminiumcorrosionproductsunderthepaint.

ProbableCauses:Pinholesinthecoating.Porosityofflame/arcsprayedaluminium.Insufficient
coatingthickness.

Prevention:Usecorrectlyformulatedcoatingsystemappliedatthecorrectthicknessasaclosed
film.

Repair:Blastcleanandrecoat.

ApplicationDefects
Description:Defectsassociatedwithapplicationbybrushe.g.brushhairsinthecoating,
contaminationfromrollers,fingeringandspatteringfromsprayapplication.

ProbableCauses:Poorqualitybrushesandrollers,incorrectbrushandrollermaterials,incorrect
spraysetupandinadequatecareduringapplication.

Prevention:Usegoodqualityequipmentofthecorrecttypeandfollowthedatasheetguidelines.

Repair:Repairisrelatedtothetypeandextentofthedefectbutoftenrubbingdownandrecoating
isadequate.

Bittiness
(alsoknownasPeppery,SeedyorSeediness)
Description:Filmcontaminatedbyparticlesofpaintskin,gel,flocculatedmaterialorforeignmatter
whichprojectabovethesurfaceofthepaintfilmtogivearoughappearance.ThetermPepperyis
usedwhenthebitsaresmallanduniformlydistributed.

ProbableCauses:Themaincauseiscontaminationwithinoronthesurfaceofthepaintfilm.This
canbepaintskin,gelledparticles,airbornematerialandgritorcontaminationfrombrushes,
rollersetc.

Prevention:Usecleanapplicationequipmentandcleanworkingenvironment.Usenew,
uncontaminatedpaint.Followgoodpaintingpractices.

Repair:Repairdependsonsizeandextentofproblem.Abradeorcompletelyremovethe
contaminatedlayerandrecoat.

Bleaching
Description:Totallossofcolourofacoating.

ProbableCauses:Weatheringorexposuretochemicals.

Prevention:Usecolourstablepigmentsorasystemwhichwillwithstandthechemical
environment.

Repair:Removebleachedcoatingorabradeandrecoatusingamoresuitablecoatingsystem.

Bleeding
(alsoknownasBleedThrough)
Description:Stainingofapaintfilmbydiffusionofasolublecolouredsubstancefromthe
underlyingpainttogiveundesirablediscolorationorstaining.Oftenseenwherebituminousortar
basedproductsareovercoatedwithtopcoatsinwhichthetarorbitumenissoluble.Alsooccurs
withemulsionpaints.

ProbableCauses:BleedThroughisgenerallyafullorpartialredissolvingofthepreviouscoator
aningredientofapreviouscoatandcanoccurwhenstrongsolventsareusedinthetopcoats.

Prevention:Usecorrectcoatingspecificationandmaterials.Usecompatiblematerials.Use
appropriatesealercoatifpossible.

Repair:Removestainedorcontaminatedlayer.Applyasuitablesealercoatwhichwillpreventthe
diffusionofsolublecolouredmaterialfrombeneath.Itmaybepossibletoapplyasealercoat

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withouttheremovalofthestained/contaminatedlayer.

Blistering(General)
Description:Domeshapedprojectionsorblistersinthedrypaintfilmthroughlocallossof
adhesionandliftingofthefilmfromtheunderlyingsurface.Blistersmaycontainliquid,vapour,
gasorcrystals.

ProbableCauses:Manymechanismscanbeinvolvedincludingosmoticgradientsassociated
withsolublesalts,solublepigments,corrosionproducts,retainedsolventsandsolventsfrom
cargoes.Nonosmoticblisteringassociatedwithelectroendosmosis,cathodicdisbonding,
thermalgradientsrelatedtocoldwalleffectsandcompressivestress.

Prevention:Ensurecorrectsurfacepreparationandapplication.Applyasuitablecoatingsystem
aftertestingforsolublesalts.Considerthepossibilityofthedifferentblistermechanismsinthe
particularenvironment.

Repair:Dependinguponsizeandtypeofblistering,removeblisteredareasorentirecoating
systemandrepairorfullyrecoat.

BlisteringIntercoat
Description:Domeshapedprojectionsorblistersinthedrypaintfilmthroughlocallossof
adhesionfromanunderlyingcoating.

ProbableCauses:Commonlythepresenceofsolublesaltcontaminationbetweencoatsor
solublematerialintheunderlyingcoats.

Prevention:Ensurethattestsforsolublesaltsarecarriedoutifcontaminationissuspectedand
freshwaterwashifnecessary

Repair:Dependinguponsizeandtypeofblistering,removeblisteredareasorentirecoating
system,freshwaterwashandrepairorfullyrecoat.

BlisteringNonOsmotic
Description:Domeshapedprojectionsorblistersinthedrypaintfilmthroughlocallossof
adhesionfromthesteelsubstrate.

ProbableCauses:Nonosmoticblisteringassociatedwithelectroendosmosis,cathodic
disbonding,thermalgradientsrelatedtocoldwalleffectsandcompressivestress.Where
electroendosmosisisinvolved,theblisteringisoftenseenasacircularpatternofblistersarounda
coatingdefectwherethesubstrateisexposed.

Prevention:Ensurecorrectsurfacepreparationandapplication.Applyasuitablecoatingsystem
afterconsideringthepossibilityofthedifferentblistermechanismsintheparticularenvironment.

Repair:Dependinguponsizeandtypeofblistering,removeblisteredareasorentirecoating
systemandrepairorfullyrecoat.

BlisteringOsmotic
Description:Domeshapedprojectionsorblistersinthedrypaintfilmthroughlocallossof
adhesionfromanunderlyingcoating.

ProbableCauses:Osmoticblisteringiscommonlyassociatedwiththepresenceofsolublesalts,
solublepigments,solublecorrosionproducts,retainedsolventsortheabsorptionandretentionof
lowmolecularweightwatermisciblesolvents,typicallyfromthecarriageofchemicalcargoes.

Prevention:Ensurecorrectsurfacepreparationandapplicationandfollowworkingprocedures
forventilationetc.Applyasuitablecoatingsystemaftertestingforsolublesalts.Considerthe
possibilityofthedifferentblistermechanismsintheparticularenvironment.

Repair:Dependinguponsizeandtypeofblistering,removeblisteredareasorentirecoating
system,freshwaterwashandrepairorfullyrecoat.

Bloom(Blush)
Description:Ahazydepositonthesurfaceofthepaintfilmresemblingthebloomonagrape,
resultinginalossofglossandadullingofcolour.

ProbableCauses:Paintfilmexposedtocondensationormoistureduringcuringespeciallyatlow
temperature(commonphenomenonwithaminecuredepoxies).Incorrectsolventblendcanalso
contributetoblooming.

Prevention:Applyandcurecoatingsystemsundercorrectenvironmentalconditionsandfollow
themanufacturersrecommendations.

Repair:Removebloomwithcleanclothorsuitablesolventcleaners.Ifnecessary,apply
undercoat/topcoatfollowingmanufacturersrecommendations.

Bodying
Description:Anincreaseintheconsistency/bodyofacoatingthatoccursduringmanufactureor
storageoftenincreasingtheviscositytoapointthatitisunusable.

ProbableCauses:Incorporationoftoomuchthixotropeorpoorstorageconditions

Prevention:Correctrawmaterialcontrolandcorrectstorage.

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Repair:Thecoatingisoftenunusable.

Bridging
Description:Thecoveringoverofunfilledgapssuchascracksorcornerswithafilmofcoating
material.Thisintroducesaweaknessinthepaintfilmwhichmaycrackorflakeoff.

ProbableCauses:Poorapplication.Highviscositypaintsystem.Failuretobrushpaintinto
cornersandoverwelds.

Prevention:Brushapplyastripecoatintocornersandweldsandfillallcracksorweldthemprior
toapplicationofthefullcoatingsystem.

Repair:Removeallloosepaint,abradethesurface,applyastripecoatbybrush,fillandrecoat.

BrushMarks
(alsoLaddering,LaddersorRopiness)
Description:Undesirableridgesandfurrowswhichremaininadrypaintfilmafterbrush
application,wherethepaintfilmhasnotflowedout.Maybefoundasacrosshatchpattern
(Laddering)wherealternatecoatshavebeenappliedinoppositedirections.Pronouncedbrush
marksareknownasRopiness.

ProbableCauses:ViscosityofmaterialmaybetoohighforbrushapplicationIncorrectthinners
usedInadequatemixingorpoorapplicationtechniquepainthaspoorlevelingpropertiestwo
packpaintsmayhaveexceededapplicationpotlife.

Prevention:Usebrushinggradeofpaintandapplyadequatethickness.Thinpainttobrushing
viscosity.Usewithinpotlife.

Repair:Dependingonextentofbrushmarks,thoroughlyabradesurfaceandrecoatwithsuitable
viscositypaint.

BubblesOrBubbling
Description:Bubbleswithinapaintfilmappearassmallblisters.Thesemaybeintactorbroken
(toleaveacrater).Canbefoundinexcessivelythickpaintfilms,especiallyifsprayapplied,and
alsowithrollerapplication.Thisshouldnotbeconfusedwithblistering.

ProbableCauses:Trappedair/solventwithinthecoatingwhichisnotreleasedbeforethesurface
dries.Airentrainmentduringmixing.Highambienttemperatureduringapplication.Alsoseen
whenovercoatingantifoulingwithoutremovaloftheleachedlayerandzincsilicates.Canbe
foundwithfactoryappliedcoatingswhereapplicationisbydipping,electrodepositionorroller
coating.

Prevention:Sprayapplicationadjustviscositywiththinnersandfollowdatasheetrequirements
formaximumapplicationtemperature.Usecorrectmixingequipmenttoensureairisnotstirredin
duringmixing.Applyamistcoat.Adddefoamingagenttoemulsionpaints.

Repair:Dependingonextentandseverityofbubbling,abradeorremovetheoffendingcoat(s)
andrecoat.

CargoDamage
Description:Deformationorremovalofacoatingbyphysicalactionorchemicalaction

ProbableCauses:Anexampleofphysicalactionistheabrasivecontactofahardangularcargo
ontheholdsofabulkcarrierandanexampleofchemicalactionisthatofanaggressivechemical
cargoonatanklining.

Prevention:Useanabrasiveresistantcoating(inmostcasesthiswillreduce/limitbutnotprevent
theabrasion)oracoatingcompatiblewiththecargotobecarried.

Repair:Inthecaseofisolatedmechanicaldamage,spotrepairandtouchup.Inthecaseof
extensivedamageblastcleanandrecoatmayberequired.

CathodicDisbonding
Description:Blisteringanddelaminationofacoatingsystemaroundbaresteelareasandcoating
defectsassociatedwithcathodicprotectiononburiedpipelines,immersedstructuresandthehulls
ofships.

ProbableCauses:Highovervoltageprincipallyfromimpressedcurrentsystemsbutalsotoa
lesserextentwithsacrificialanodeswhenthenumberofanodesisexcessive.Factorsare
incorrectinstallation,poormonitoring,andincompatiblecoatingsystems.

Prevention:Useawelldesignedcathodicprotectionsystem,regularlymonitoredwithwellplaced
referenceelectrodesandapplicationofanalkaliresistantcoatingsystem.

Repair:Eliminatethesourceoftheoverprotection.Blastcleantheaffectedareasandapplya
suitablecoatingsystem.

Chalking
Description:Afriable,powderylayeronthesurfaceofapaintfilm.Achangeofcolourorfadingis
alsoseen.Chalkingratesvarywithpigmentconcentrationandchoiceofbinder.Chalkingisa
knowncharacteristicofcertainpaintse.g.epoxypaints.

ProbableCauses:Disintegrationofthepaintbinderonexposuretoweatheringand/orUVlight.

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Prevention:Applyasuitabletopcoatwithhighresistancetochalking,andwithUVresistance.

Repair:Removeallpowderydepositsbywiping,scrubbing,highpressurewashingorabrasion.
Wipeloosematerialoffandapplyachalkresistanttopcoat.

Checking
Description:Finecrackswhichdonotpenetratethetopcoatofapaintsystem.Somechecking
canbesominutethatitisimpossibletoseewithoutmagnification.

ProbableCauses:Typicallyaformulationand/oraspecificationproblem.Aswithcracking,
stressesaredevelopedwhichcausethesurfaceofthepaintfilmtobecomebrittleandcrack.
Limitedpaintflexibility.

Prevention:Useacorrectlyformulatedcoatingsystem.

Repair:Abradeandcleansurfacethenapplyanundercoat/topcoattosuit.

Cheesiness(SoftCoating)
Description:Coatingremainssoft,evenafterprolongeddryingtime.

ProbableCauses:Wrongmixingratiofortwopackpaints.Toolowadrying/curingtemperature.
Excessivesolventretainedwithinthecoating.

Prevention:Ensureadequatemixingoftwopackpaints.Onlyusetherecommendedamountof
thinners.Applyandcurethecoatingundercontrolledenvironmentalconditions.

Repair:Removeallsoftcoatingsandapplysuitablecoatingsystemortopcoattocoating
manufacturersrecommendations.

ChemicalExposure
Description:Chemicalbreakdownofacoatingafterexposuretoaggressivechemicals.

ProbableCauses:Thereactionofacoatingwithachemicaloratmosphere(eitherorganicor
inorganic)thatitisnotresistantto.

Prevention:Usecoatingsystemssuitablefortheenvironmentorpreventthechemicalfrom
reachingthecoatedsurface.

Repair:Willdependontheextentoffailurebutremovalorneutralizationofthechemicaland
freshwaterwashingessential.Useachemicallyresistantcoatingandconsiderisolationfromthe
sourceofthechemical.

Cissing
Description:Surfacebreaksinawetpaintfilm,wherethepainthasrecededtoexposethe
underlyingsubstrate.Thepaintisunabletowetoutthesubstrate.Canbeverylarge.

ProbableCauses:Surfacecontaminationbyeithermoistureorforeignmattersuchasoil,grease,
siliconeetc.Alsoknowntohappenwhenincorrectsolventblendshavebeenused.

Prevention:Ensuresurfaceiscleanandfreefromgrease,oilandforeigncontaminantspriorto
applicationofcoating.

Repair:Abradeandthoroughlycleanthecontaminatedsurfaceorremovethecoatingtoachieve
acleansurface.Reapplythecoatingsystemtothecoatingmanufacturersrecommendations.

Cobwebbing
Description:Theproductionoffinefilamentsinsteadofnormalatomisedparticleswhensome
solutionsofhighmolecularweightpolymersaresprayed.Traditionallywhenapplyingchlorinated
rubbercoatingsbyconventionalspray.

ProbableCauses:Toohighaviscositywithsometypesofpolymersolutions.Willoccurwith
chlorinatedrubberatalmostanyviscosity.

Prevention:Reducethesprayingviscosity.Selectamoresuitablesolventblend.Changethe
sprayingconditions.

Repair:Abradetoremoveallaffectedmaterialandrecoat.

Cracking
Description:Thesplittingofadrypaintfilmthroughatleastonecoattoformvisiblecrackswhich
maypenetratedowntothesubstrate.Crackingcomesinseveralforms,fromminutecrackingto
severecracking.

ProbableCauses:Crackingisgenerallyastressrelatedfailureandcanbeattributedtosurface
movement,ageing,absorptionanddesorptionofmoistureandgenerallackofflexibilityofthe
coating.Thethickerthepaintfilmthegreaterthepossibilityitwillcrack.

Prevention:Usecorrectcoatingsystems,applicationtechniquesanddryfilmthicknesses.
Alternatively,useamoreflexiblecoatingsystem.

Repair:Abradetoremoveallcrackedpaint.Correctlyreapplythecoatingsystemoruseamore
flexiblesystemandonelesspronetocracking.

CrackingAtWelds
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Description:Paintcoatingswithvisiblecracksatweldseamswhichmaypenetratedowntothe
substrate.

ProbableCauses:Crackingisgenerallyastressrelatedfailureandcanbeattributedtosurface
movement,ageing,absorptionanddesorptionofmoistureandgenerallackofflexibilityofthe
coating.Thethickerthepaintfilmthegreaterthepossibilityitwillcrack.Alsooccurswhenthe
adhesionofthecoatingisinsufficienttobearthestress.

Prevention:Usecorrectcoatingsystems,applicationtechniquesanddryfilmthicknessesorusea
moreflexiblecoatingsystem.

Repair:Abradetoremoveallcrackedpaint.Correctlyreapplythecoatingsystemoruseamore
flexiblesystemandonelesspronetocracking.

Cratering
Description:Theformationofsmallbowlshapeddepressionsinthepaintfilm.Nottobeconfused
withCissing.

ProbableCauses:Trappedairorsolventbubbleswhichhavebursttoleavesmallcratersasthe
coatingdries.Thecoatinghasinsufficienttimetoflowintoauniformfilm.

Prevention:Improvespraytechnique,applyamistcoatandavoidairentrainmentduringmixing.
Addthinnersasrecommendedbythepaintsupplier.

Repair:Abradeandcleanthesurfaceandrecoat.

Crazing
Description:Similartocheckingbutthecracksaregenerallywiderandpenetratedeeperintothe
film.

ProbableCauses:Applicationtemperaturetoolow,incompatibilitywithpreviouscoating,ageing
andhighfilmthickness.

Prevention:Applyathinnercoatofpaint,addslowerdryingsolvent,checkapplicationanddrying
conditionsarecorrectforthepaintsystemusedandcheckcompatibility.

Repair:Abradeandcleanthesurfaceandrecoat.

Crowsfooting
Description:Thedevelopmentofsmallwrinklesinthepaintfilmwhichoccurinapattern
resemblingthatofacrowsfoot.

ProbableCauses:Usuallyduetothesurfacedryingrapidlytoformaskinwhichthenwrinklesas
solventslowlyevaporatesfromthesoftunderlyingpaint.

Prevention:Applyathinnercoatofpaintaddslowerdryingthinners,checkapplicationand
dryingconditionsarecorrectforthepaintsystemused.

Repair:Abradethesurfacewhenfullydryandrecoat.

Dryspray
Description:Roughandunevenfinishtothesurfaceofthepaintfilmwheretheparticlesare
insufficientlyfluidtoflowtogetherandareoftenpoorlyadhered.

ProbableCauses:Incorrectsprayapplicationi.e.gundistance.Alsoassociatedwithfastdrying
productsandtoohighanapplicationtemperature.

Prevention:Usecorrectcoatingapplicationequipmentandtechniques.Useaslowerdrying
solventorsolventblend.Followrecommendedapplicationprocedures.

Repair:Abradeandremoveanyloosedrysprayandreapplycoatingortopcoat.

EdgeCorrosion
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ProbableCauses:Lowfilmthickness,sharpedges,lackofstripecoatsandflowawayfromthe
edges.

Prevention:Ensurethatalledgesareradiused,stripecoatsareappliedandthecoatinghasgood
edgeretention.

Repair:Removecoatingbyabrading,radiustheedgesandreapplythecoatingsystemwith
adequatestripecoats.

Efflorescence
Description:White(powdery)substanceonthesubstrateofconcrete,brick,masonryandplaster.
Theefflorescence,whichcomesfromthemigrationofsalts,canliftthepaintfromthesubstrate.

ProbableCauses:Solublesaltswithinthesubstrate.Moisturebringsthesaltstothesurfaceofthe
substrateresultingincoatingadhesionfailure.

Prevention:Ensuresurfaceismoisturefree,cleanandsuitableforapplicationofthecoating
system.Removeoreliminatethesourceofmoisture.

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Repair:Removeallpowderysubstancesandthoroughlycleanthesurface.Applyasuitable
sealerandcoatingsystemformulatedforconcrete,masonryetc.

Erosion
Description:Selectiveremovalofpaintfilmsfromareasorhighspots.

ProbableCauses:Thewearingawayofthepaintfilmbyvariouselementssuchasrain,snow,
wind,sandetc.Foundtobemoreprominentonbrushappliedcoatingsbecauseoftheuneven
finish.

Prevention:Useasuitablecoatingsystemwithresistancetosurfaceerosion/abrasion.

Repair:Cleansurfacefreefromcontaminationandapplyacoatingsystemformulatedandtested
forthespecificenvironment.

Exudation
Description:Theappearanceofanoillikefilmonthesurfaceofthecoatingafterdrying.Also
describedassweatingbutnottobeconfusedwhenthetermisusedtoexplaincondensationona
surface.

ProbableCauses:Migrationofacomponentofthecoatinge.g.plasticizer,additive,orcuring
agentthatremainedunreacted.Oftenassociatedwithpoorenvironmentalconditionsduringor
afterapplication.

Prevention:Applyundergoodenvironmentalconditionsanduseamoresuitablecoating.

Repair:Dependsontheextentofthedefectbutmayberesolvedbysolventwashingandre
applicationofasuitabletopcoatundercontrolledenvironmentalconditions.

Fading
Description:Discolourationorgradualdecreaseincolourofpaintwhenexposedto
sunlight/weather.Maybeaccompaniedbylossofgloss.Insomesituationsitmayresemble
chalkingbutwithoutthepowderysurface.Fadingtendstoaccelerateinthepresenceofmoisture.

ProbableCauses:Incorrectpigmentationuseofnonlightstableorganicpigmentsatmospheric
contaminationporoussubstrate.

Prevention:UsecorrectcoatingsystemswhichresistUVlightandfading.Useacoatingwithlight
stablepigments.

Repair:Abradeandcleanthesurfaceandapplyalightstablecoatingsystem.

FatEdge
Description:Anaccumulationofaridgeofcoatingatanedgeofthearticlebeingcoatedoften
occurringduringdrainageafterdipapplication.

ProbableCauses:Rheologyofthecoatingnotsuitablefordipapplication.

Prevention:Reformulateoruseamoresuitablecoating.

Repair:Abradetheareaandrecoat.

FeatherEdging
Description:Bevelling/taperingtheedgesofarepairareaofacoatingbyabradingtogradually
reducethethicknessandexposethedifferentunderlyinglayers.

ProbableCauses:Untreatededgesofspotblastcleanedrepairareas.

Prevention:Abradealledgesofspotblastcleanedrepairs.Thisisonlypracticalonsmallareas.
Onextensivespotblastingitisimpractical

Repair:Bevel/tapertheedgestograduallyexposepreviouscoatsandrecoat.
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Description:Randomthreadsofcorrosionthatdevelopbeneaththinlacquersandothercoating
filmsfromagrowingheadorpoint.Oftenseenonoldtinfoodcans,withthinelectroplatingbut
alsoonpaintedaluminiumandothersurfaces.

ProbableCauses:Contaminationonthemetallicsubstrateordamagetothecoatingwhichallows
acorrosioncelltodevelopatthetipandadvanceunderthecoating.

Prevention:Ensurenocontaminationexistsonthesubstratepriortocoatingapplication.

Repair:Removealltracesofcorrosionproductsandnonadheringcoatings.Abrade,cleanand
coattomanufacturersrecommendations.

FishEyes
Description:Smallquasicircularareasofsubstratethatareexposedthroughtheappliedcoating
immediatelyafterapplicationandwhichhaveattheircentreasourceofcontamination.

ProbableCauses:Surfacecontaminationintheformofsmallspotsofwax,silicone,greaseor
particlesfromcontaminatedairlines.

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Prevention:Thoroughlydegreasethesurfaceandmaintainequipment.

Repair:Abradetheaffectedarea,degreaseandreapplythecoatingsystem.Inautomotive
applicationsfisheyeeliminatorscanbeused.

Flaking
Description:Aformofadhesionfailurewherepaintflakesfromthesubstrate.Afamiliarsighton
woodsubstratesandongalvanising.

ProbableCauses:Incorrectpaintsystemused.Eithernoneorincorrectpretreatmentusedfor
certainsubstratesi.e.nonferrousorgalvanised.Alsopoorapplicationtechniques.Mayalsobe
attributedtodifferentialexpansionandcontractionofpaintandsubstratee.g.wood.Canbethe
resultofageingofthepaintsystem.

Prevention:Usecorrectcoatingsystemandpretreatment.

Repair:Removeallflakingcoatinguntilafirmedgecanbeachieved.Abrade,sweepblastand
cleanoverallandapplysuitablecoatingsystemtocoatingmanufacturersrecommendations.

Flocculation
Description:Thedevelopmentoflooselycoherentpigmentagglomeratesinacoatingmaterial.

ProbableCauses:Nonuniformpigmentdispersionwhichresultsinthepigmentsforming
agglomerations.Unsuitablethinnersorinadequatemixing.Canalsooccurinmanufacturing.

Prevention:Ensureonlyproperlyformulatedandmixedproductsareused.Userecommended
thinners.

Repair:Removecoatingwhereflocculationisvisible.Abradeandcleanthesurfaceandapplya
properlyformulatedandmixedcoatingsystem.

Flooding
Description:Adefectwhichappearssoonafterapplicationduetopigmentseparation.Thevisual
appearanceisadeepeningofthecolour.Theaffectedareadriestoadeepershadethanthe
remainderofthesurface.

ProbableCauses:Pigmentseparationandsettlement.

Prevention:Usecorrectlyformulatedproducts.

Repair:Lightlyabradeandcleanandthenrecoatwithasuitablyformulatedmaterial.

Flotation
Description:Occursincolouredmaterialscontainingmixturesofdifferentpigments.Itclosely
resemblesflooding,althoughamottledorstreakyeffectisproducedwhenthedifferentpigments
separate.

ProbableCauses:Themottledeffect,whichisvisibletotheeye,iscausedbyseparationofthe
differentcolouredpigments.Itmayalsoresultfromtheadditionofexcessivethinners.

Prevention:Usecorrectlyformulatedproducts.Donotoverthinwithsolvent.

Repair:Abradeandcleanoverallandapplyasuitablesealerortopcoat.

Galvanising(Lossofadhesionofcoating)
Description:Lossofadhesiontoagalvanizedsubstrate.

ProbableCauses:Incorrectsurfacepreparationorabsenceofanetchprimer/TWash.

Prevention:Abradeweatheredgalvanizingorapplyetchprimer/TWashtofreshgalvanizing
afterdegreasing.

Repair:Removedetachedpaint,degrease,freshwaterwashandabradeweatheredgalvanizing
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GrinningorGrinningThrough
Description:Theunderlyingsurfaceisvisiblethroughthepaintfilmduetoinadequatehiding
powerofthecoatingmaterial.ThisissometimescalledGrinningThrough.Oftenseenwhere
darkcoloursareovercoatedwithlightercolours.

ProbableCauses:Lowfilmthicknessofpenultimatecoat.Pooropacityandcoveringpowerof
topcoat.Strongcolourofprimer/undercoats.

Prevention:Applyadequatedryfilmthicknessbetweenindividualcoats.Useopaquecoatings
withgoodopacity.

Repair:Applyadditionalcompatiblecoatstocleansurface.

GritInclusions
Description:Particlesofgritanddustembeddedwithinthecoatingsystem.Theparticleswillrust
ifferrous.

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ProbableCauses:Failuretoremoveusedgritfromthesurfacepriortoapplicationofthepaint.
Contaminationofthewetprimerorundercoatwithgritfromotherblastcleaningoperations.
Windblowngritparticlesadheringtothetopcoat.

Prevention:Ensureallusedgritisremovedbeforeapplicationoffreshpaint.Donotcarryout
blastcleaningwhilstthereiswetpaintonnearbysurfaces.Ensurethanallcansofpaintand
brushesetc.areprotectedduringblastcleaningoperations.

Repair:Abradeorblastcleanthesurfacetoremoveallgritcontamination,thoroughlycleanthe
surfaceandrecoat.

Growth(onthesurfaceofapaintfilm)
Description:Growthandattachmentoforganismstothesurfaceoffinishedproducts.Thesevary
inform,sizeandlifespan,e.g.algae,mossesetc.

ProbableCauses:Naturalorganismsassociatedwithmoist,wetorimmersedconditions.Growth
maycontinueafterattachment.

Prevention:Usecorrectcoatingspecificationandproductssuitablefortheenvironment.Where
practical,cleanregularlytopreventbuildupofmossandalgae.

Repair:Cleanandremoveallgrowth,abradethesurfaceandapplyasuitablecoatingsystem.

HeatDamage
Description:Discolouration,detachmentand/orblisteringandgeneraldegradationofapaint
film.

ProbableCauses:Effectofhightemperatureoftenappliedtothereversesideofasteelplatefrom
burning,weldingorfire.

Prevention:Ensurethatallwelding/burningiscompletedpriortopainting.

Repair:Abradesmallareasorblastcleanlargeareaspriortoreinstatingthecoatingsystem.

ImpactDamage(Starcracking)
Description:Crackswhichradiatefromapointofimpact.

ProbableCauses:Impactdamagetoarelativelybrittlecoating.Oftenseenonglassfibre
reinforcedplastics.Alsooccurswhensteelisdeformedbyimpact.

Prevention:Preventimpactdamage.

Repair:Abradealldamagedareasandrecoat.

IncorrectCoatingSystem
Description:Anunsuitableorincompatiblecoatingsystemhasbeenusedwhichresultsinrapid
failure.

ProbableCauses:Useofincompatibleorunsuitablecoatingmaterialsfortheservicerequired.

Prevention:Usecorrectcoatingspecificationandmaterials.Ensurethatdifferentcoatsare
compatiblewitheachother.

Repair:Removealldefectivecoatingandapplycorrectcoatingsystemtomanufacturers
recommendations.

IncorrectCoatingThickness
Description:Acoatingsystemthathasbeenappliedatinadequatethicknessoftenleadingto
prematurebreakdown.

ProbableCauses:Poorsprayapplication,poorqualitycontrolanddifficultaccess.

Prevention:Improvesprayapplicationandqualitycontrol.
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Repair:Abradeareaandoverlapsandreapplytothecorrectthickness.
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IntercoatContamination
Description:Thepresenceofcontaminationbetweencoatsinamulticoatsystem.

ProbableCauses:Thecontaminationcouldbepresentduetoinadequatewashingdown,salts
fromweatheringofshopprimerordepositsfromnearbyoperations.

Prevention:Carefullyinspectandtestthesurfacebeforepaintapplicationandwashdownwith
freshwaterifrequired.

Repair:Abradetoremovepoorlyadherentpaint,freshwaterwashandrecoat.

Knotting
Description:Bleedthroughofresin/sapfromknotsintimberandstainingofthesurfacewith
brownishmarks.

ProbableCauses:Knotsnottreatedwithknottingagentbeforepainting.

Prevention:Treatknotswithshellacbasedsolution.
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Repair:Cleanareawithmethylatedspirit,abradeandrecoat.

LaminationsOrShelling
Description:Subsurfaceplanarmetallicdefectsappearingasisolatedthinstripsorlayerswith
pooradhesiontotheparentmetal.Overpaintingwithouttreatmentresultsinpaintbreakdown,
rustingandruststaining.

ProbableCauses:Laminationsareassociatedwithnonmetallicinclusionswhichhavebeen
deformedduringtherollingprocessandruninthedirectionofrolling.Theyareoftenonlyvisible
afterblastcleaning.

Prevention:Usegoodqualitysteelplateandensurepropersurfacepreparationiscarriedout.

Repair:Grindalllaminationstoremovethemandblastcleanthesurfaceandrecoat.

MechanicalDamage
Description:Paintremovalbyscrapingandscratchingfromcontactwithexternalobjects.

ProbableCauses:Contactwithanchorchains,fenders,groundinganduseofchainsratherthan
slingsforlifting.

Prevention:Useabrasionresistantcoatingstominimizedamageanduseappropriatelifting
equipment.

Repair:Mechanicallycleansmallareasandblastcleanlargerareaspriortorecoating.

Milkiness
Description:Amilkywhitesurfaceappearancethatisapparentshortlyafterapplicationandoften
seenontransparentvarnishfilms.

ProbableCauses:Moisturecondensingonthefilminhumidconditionswhenthesteel
temperatureisbelowthedewpoint.Canbeaggravatedbyincorrectsolventbalance.

Prevention:Ensureenvironmentalconditionsareasrecommendedinthedatasheet.

Repair:Applyheattotheaffectedareaorrecoataftertheenvironmentalconditionshavebeen
corrected.

Millscale
Description:Theblue/blackthinlayerofironoxidesformedonthesteelsurfaceduringthehot
rollingprocess.

ProbableCauses:Millscaleisnotuniformandnotwelladherenttothesteel,henceifpainted
overwilldetachfromthesteelsubstratetogetherwiththepaintasmoistureladenairpenetrates
beneathand/ordifferentialexpansion/contractionoccurs.

Prevention:Abrasiveblastcleantoremovethemillscaleandimpartasurfaceprofile.

Repair:Abrasiveblastcleanandapplyasuitablecoatingsystem.

Misses/Skips/Holidays
Description:Exposedareasofsubstratewhentheintentionwastocoattheentirearea.Couldbe
confinedtoasinglecoatinamulticoatpaintsystem.

ProbableCauses:Poorapplicationtechniques.Lackofqualitycontrol.Pooraccessanddesign.

Prevention:Usecorrectapplicationtechniques.Applygoodpaintingpractices.Usequalified
inspectors.

Repair:Applycoatingstosuitablypreparedandcleanedsubstratestooriginalspecificationand
manufacturersrepairprocedures.

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Description:Failuretoapplythetopcoatleavingtheundercoatexposed.
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ProbableCauses:Poorcoatingapplicationandqualitycontrol.Inadequatedryfilmthickness.

Prevention:Thoroughlyinspectallsurfacestoensureeachcoathasbeencorrectlyapplied.

Repair:Abradethesurfaceandeitherapplythetopcoat,oranadditionalundercoatandtopcoat,
inaccordancewiththepaintsuppliersrecommendations.

MudCracking
Description:Thedriedpaintfilmhastheappearanceofadriedoutmudflat.Thecracksappear
asanetworkthatcanvaryinsizeandamount.

ProbableCauses:Generallyoverapplicationofheavilypigmentedprimerssuchasinorganic
zincsilicatesorwaterbasedcoatings,althoughcanoccurwithotheroverthicksystems.

Prevention:Onlyapplytherecommendedcoatingthickness.Userecommendedapplication
techniqueswithsuitablyformulatedproducts.

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Repair:Removeallcrackedandflakingpaintbacktoasoundbase.Abradeandcleanorblast
cleanthesurface.Reapplycoatingtomanufacturersrecommendations.

OrangePeelalsoknownasPockmarking
Description:Auniformpockmarkedappearance,inparticularofasprayappliedcoatinginwhich
thesurfaceofthepaintfilmresemblestheskinofanorange.

ProbableCauses:Failureofthepaintfilmtoflowout.Usuallycausedbypoorapplication
techniques,byincorrectsolventblendortoohighthixotropy.

Prevention:Usecorrectapplicationtechniqueswithsuitablyformulatedproducts.

Repair:Whereaestheticsareofconcern,abradeoverall,cleanandrecoat.

Overspray
Description:Smallparticlesofpaintadheringtothesurfaceofapreviousdrycoat,generally
adjacenttotheareabeingsprayed.Oftenappearsasapebblysurface.

ProbableCauses:Particlesofwetpaintfallingoutsidethespraypatternasmisapplicationtoan
adjacentsurface.Sprayapplicationunderwindyconditions.

Prevention:Spraypaintundersuitableenvironmentalconditions.Adjustspraypatternto
minimiseoverspray.

Repair:Beforecuringordrying,removebydrybrushingfollowedbysolventwipe.Aftercuring,
abradeandapplyafurthercoat.

Peeling
Description:Similartoflaking,althoughpeelingtendstobeassociatedwithsoftandpliablefresh
coatingswhichcanbepulledawayfromorspontaneouslyflakeawayfromthesubstrateorfrom
betweencoats,duetolossofadhesion.

ProbableCauses:Peelingisthereductioninbondstrengthofthepaintfilmduetocontamination
orincompatibilityofcoats.

Prevention:Usecorrectcoatingsystemandspecificationappliedtocleananduncontaminated
surfaces.

Repair:Removeallsoftandpliablecoatingbacktoafirmedgeortotalremoval.Abrade,clean
andapplysuitablecoatingsystemtocoatingmanufacturersrecommendations.

Pinholes
Description:Theformationofminuteholesinthewetpaintfilmduringapplicationanddrying,due
toairorgasbubbleswhichburst,givingrisetosmallcratersorholeswhichfailtocoalescebefore
thefilmhasset.

ProbableCauses:Solventorairentrapmentwithinapaintfilm.Acommonproblemwhencoating
poroussubstratesuchaszincfilledprimers,zincsilicatesandmetalsprayedcoatings.Pinholes
canalsobecausedbyincorrectsprayapplicationorincorrectsolventblend.

Prevention:Usecorrectapplicationtechniqueswithsuitablyformulatedproducts.Correctsolvent
blendsandenvironmentalconditions.Checksprayequipmentanddistanceofspraygunfromthe
surface.Applyamistcoat.

Repair:Abrade,cleanoverallandapplysuitabletiecoat/undercoatandtopcoatasnecessary.

PrimerDegradation
Description:Deteriorationofashopprimerduringweatheringintheformofrustrashingandsalt
formationinthecaseofzincsilicateprimers.

ProbableCauses:Lowfilmthickness,excessiveexposureperiodsandharshenvironmental
conditions.
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Prevention:Ensurethataneven,adequatefilmthicknessisappliedandtheexposureperiodis
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Repair:Dependingontheextent,thesurfaceiseitherpreparedbymechanicalcleaning(small
areas)orblastcleaning(largeareas)priortoapplicationofthecoatingsystem.

RainDamage
Description:Cratersandwatermarksonthesurfaceofthepaintfilmcausedbyrainorheavy
condensation.

ProbableCauses:Rainfallingonafreshlypaintedsurfacecausescraterstoformonthesurface
beforeithashardenedsufficiently.

Prevention:Allowcoating(wherepracticable)tosurfacehardenpriortoexposuretorainorheavy
condensation.

Repair:Abrade,cleanallsurfacedamageareasandapplyoverallundercoat/topcoat.

RippledCoating
Description:Arippledeffectonthesurfaceofthepaint.

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ProbableCauses:Strongwindblowingacrossthesurfaceofwetpaintcausesittoripple.Where
thisisontheunderside,theripplescanhangdownintheformofsmallstalactites.Canalsobe
causedbypoorapplicationtechniques.

Prevention:Donotapplypaintunderunfavourableconditions.Usecorrectapplicationequipment
andworkmanship.

Repair:Whenmildripplesareseen,abradethesurfaceandrecoat.Wherethisisamajoreffect,
removethecoatingsandrecoat.

Rot(wood)
Description:Dampandrottenwoodexposedbysplitting,flakingandcrackingofpaint.

ProbableCauses:Generallypoormaintenanceorapplicationoversoftandrottenwood.
Occasionally,useofincorrectpaintsystem.

Prevention:Correctandongoingmaintenancetothewoodandcoating.Ensureallwooden
surfacesaresoundandfreefromrotbeforeapplicationofpaint.

Repair:Replacerottenwood,preferablywithtreatedwood.Applyasuitablecoatingsystem
formulatedforwoodsurfaces.

Runs
Description:Anarrowdownwardmovementofacoatofpaintoftenapparentfromaccumulation
ofexcessivequantitiesofpaintatirregularitiessuchascracksandholeswherethepaint
continuestoflowafterthesurroundingsurfacehasset.

ProbableCauses:Overapplicationofpaint,excessiveuseofthinners,incorrect(lackof)curing
agentorpoorworkmanship.

Prevention:Usecorrectapplicationtechniquesandapplyattherecommendeddryfilm
thickness.

Repair:Whilethepaintisstillwet,brushoutrunsandsags.(N.B.thisdoesnotrestorethesurface
properly).Whenthepainthasdried,abradeandcleandefectiveareasandapplyoverallcoator
spotrepair,asnecessary.

RustJacking
Description:Formationoflayersofrustscalethatexpand,increaseinvolumeandforcethe
matingsurfacesapart.

ProbableCauses:Penetrationofmoisturebetweenmatingsurfacesthroughdefectsinthe
coatingsystem.

Prevention:Edgesofmatingsurfacestobeadequatelycoatedandgapstobesealed.

Repair:Allcorrosionproductstoberemovedpriortotheareabeingfreshwaterwashed,
recoatedandgapssealed.

RustRashingtoThermalSprayCoating
Description:Spotsofferrousoxidedevelopwithintheporesofasprayedmetalcoatingsimilarto
rustrashingofapaintfilm.

ProbableCauses:Aphenomenonwhichcandeveloponaluminiumthermalsprayedcoatings
soonafterapplicationasmoistureisabsorbedintothemetalcoatingandreactswiththeferrous
substrate.

Prevention:Applythermalspraycoatinginacontrolledenvironment.Sealmetalsprayedsurface
immediatelyafterapplication.

Repair:Cleanrustrashinglocations,wirebrushandfreshwaterwash.Providingdryfilm
thicknessofthethermalsprayisadequate,applysealercoattocoatingmanufacturers
recommendations.
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Description:Finespotsofrustwhichappearonapaintfilm,oftenathinprimercoat.Theinitial
spotsrapidlyspreadoverthesurfaceresultinginafilmofrustthroughwhichtheindividualspots
aredifficulttodiscern.Alsofromholidays.
ProbableCauses:Lowfilmthicknessoftenincombinationwithahighsurfaceprofile.

Prevention:Ensurethatanadequatethicknessofaprimercoatisappliedtocoverthesurface
profileandcheckthatthesurfaceprofileisnottoolarge.

Repair:Cleanrustrashinglocations,wirebrushandfreshwaterwash.Largeareasmayrequire
blastcleaning.

RustSpotting
Description:Individualspotsofrustwhichappearonapaintfilmandfrequentlystartaslocalised
spottingbutrapidlyincreaseindensity.

ProbableCauses:Lowfilmthickness(morelikelycreatingrustrashing),voidsandholidays(more
likelycreatingrustrashing),butalsodefectsinthesteelsuchaslaminationsandinclusions.Too
highasurfaceprofilemaycausepenetrationofpeaksthroughapaintfilmandcauserust
spotting.Mayalsooccurfrommetalliccontaminationofacoatedsurfacebygrindingdustetc.

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Prevention:Ensurethatanadequatethicknessofaprimercoatisappliedtocoverthesurface
profile.Useathickercoatingsystemoralowerblastprofile.Protectcoatingfromcontamination
withgrindingdustetc.

Repair:Dependingontypeandextent,abradeorblastcleansurfaceafterremovalofallforeign
debris.Applyspotrepairorrecoatoverall.

RustStaining
Description:Alightstainingonthesurfaceofthepaintcausedbytheprecipitationofferrous
oxidefromadjacentexposedsteel.

ProbableCauses:Waterrunofffromarustysurfaceaboveasoundlycoatedsurface.Rust
stainingoccurswhentherustiswettedoutandcontaminatedwaterrunsoveranddiscolours
otheritemsorlocations.Usuallymoreofaneyesorethanadefect.Thecoatingitselfmaynotbe
defective,onlystained.

Prevention:Adequatedesignandsuitablemaintenance.

Repair:Removestainingwitharustremoverandapplyacosmeticcoating,asnecessary.

Sagsalsodescribedascurtains
Description:Sagsarethedownwardmovementofacoatofpaintwhichappearsoonafter
applicationandbeforesettingthatresultsinanunevenareawithathickloweredge.Theyare
usuallyapparentonlocalareasofaverticalsurfaceandinseveresituationsmaybedescribedas
curtains.

ProbableCauses:Overapplicationofpaint,excessiveuseofthinners,incorrect(lackof)curing
agentorpoorworkmanship.Could,inextremecircumstances,beaformulationproblem.

Prevention:Usecorrectapplicationtechniqueswithsuitablyformulatedproducts.

Repair:Whilethepaintisstillwet,brushoutrunsandsagsalthoughthismaynotresultinan
acceptableappearance.Whenthepainthasdried,abradeandcleandefectiveareasandapply
overallcoatorspotrepairasnecessary.

Salts
Description:Contaminationintheformofasalt.

ProbableCauses:Depositionfromacoastalsaltladenenvironment,environmentalpollutionor
weatheringofzincprimers.

Prevention:Protectitemsfromexposureduringtreatmentandfreshwaterwashbetweencoatsif
positivetestsforsaltsareobtained.

Repair:Ifsaltsaredetectedfreshwaterwashpriortocoatingapplication.

Saponification
Description:Thecoatingappearstobesoftandsticky.Canbeinsporadicisolatedspotsorasan
overalleffect.

ProbableCauses:Theformationofasoapbythereactionbetweenafattyacidesterandan
alkali.Decompositionofthebindercomponentofalkydandoilbasedcoatingsbyalkaliand
moisturefromasubstratesuchasconcreteorcementitiousrenders.Canalsooccuronzinc
substrates.

Prevention:Usecorrectcoatingspecificationsandmaterials.

Repair:Removeallsoftcoatingswheresaponificationhasoccurred,abrade,cleanandreapply
undercoat/topcoatusingnonsaponifiablematerials.

Settlement
Description:Thesedimentationofthesolidconstituentscomprisingpigmentsandextendersfrom
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ProbableCauses:Oldstock,heavilypigmentedpaintandincorrectformulationofproduct.Can
beaproblemwithzincrichprimers.

Prevention:Useproductswithinshelflife.Useadequatemixingprocedures.Keeppaintmixedor
recirculatedduringsprayapplication.

Repair:Ifavariationinshadeisproduced,abradeandreapplyensuringuniformmixingbefore
andduringapplication.

Skinning
Description:Formationofalayerofskinonthepaintsurfaceinacontainer.

ProbableCauses:Absenceofantiskinningagent,useofnonairtightcontainer,hotstorage
conditions.Oftenoccursinpartusedcans.

Prevention:Useairtightcontainerandstoreaccordingtodatasheet.

Repair:Removelayerofskinandmixuntilhomogeneous.

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3/31/2017 4.CoatingDefects:MPIGroup

SolventLifting
Description:Eruptionofthesurfaceofthepaintfilm.Wrinklingandblisteringwhichleadstoa
weaksurfaceandultimatecoatingbreakdown.

ProbableCauses:Incompatiblepaintsystemsused.Topcoatswithastrongsolventblendcan
reactwithpreviousandweakersolventblendedcoatings.Overcoatingbeforethepreviouscoat
hasadequatelyhardened.

Prevention:Usecorrectcoatingspecification,overcoatingtimesandmaterials.Conduct
compatibilitytrialswithundercoat/topcoats.

Repair:Removealldefectivecoatings.Abrade,cleanandrecoatwithcorrectcoatingsystem,
followingtherecommendedovercoatingtimes.

SolventPopping
Description:Solvent(clear)bubblesonthesurfaceofthepaintfilmsoonafterapplication.

ProbableCauses:Incorrectsolventblends,poroussurfacesandincorrectenvironmental
conditions.Highsurfacetemperature.

Prevention:Usecorrectcoatingspecificationsandmaterialsandensurecorrectapplication
techniquesandenvironmentalconditions.

Repair:Lightlyabradeandcleanthesurfaceandapplyundercoat/topcoat.

Staining
Description:Discolourationofacoatingsystem.

ProbableCauses:Contactwithasolidorliquidthatimpartsadiscolourationorstaintothe
coating.

Prevention:Avoidcontactwithsolidsandliquidsthatarepronetocausestainingorusedark
colouredcoatingswhereanystainingwouldnotbesoapparent.

Repair:Ifthestainsareonthesurfacetheymayberemovedbywashingwithwaterorchemical
cleaningagents.Ifthestainshavepenetratedthecoating,abradingafterwashingmaybe
requiredpriortorecoating.

StressCracking
Description:Paintcoatingswithvisiblecrackswhichmaypenetratedowntothesubstrate.

ProbableCauses:Stresscrackingcanbeattributedtosurfacemovement,ageing,absorptionand
desorptionofmoisture,thermalcyclingandgenerallackofflexibilityofthecoating.Thethickerthe
paintfilmthegreaterthepossibilitythatcrackingmightoccur.Oftenoccursaroundweldsand
changesinsection.

Prevention:Usecorrectcoatingsystems,applicationtechniquesanddryfilmthicknessesorusea
moreflexiblecoatingsystem.

Repair:Abradetoremoveallcrackedpaint.Correctlyreapplythecoatingsystemoruseamore
flexiblesystemandonelesspronetocracking.

StripeCoats
Description:Althoughnotadefecttheabsenceofstripecoatscanleadtoprematurebreakdown.
Acoatofpaintappliedbybrushorrollertoedges,welds,pitsandotherdifficulttosprayareas
priortoapplicationofthenextfullcoat.

ProbableCauses:Breakdowncanoccurfromareasnotstripecoatedduetothetendencyofa
coatingtoflowawayfromanedgeresultinginlowfilmthickness.(Thethirdphotographillustrates
anareaofpoorstripecoating)

Prevention:Ensureadequatestripecoatingiscarriedoutpriortoapplicationofeachfullcoat.
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Tackiness
Description:Degreeofstickinessremaininginthefilm.Althoughbeyondthewetandliquidstage,
thepaintfilmremainsasatackyandsoftsurface.Sometimesonlyapparentontouchingthe
coating.

ProbableCauses:Therearevariousreasonswhyapaintwillremaintacky:
Overthickness
Excessivethinners
Wrong(lackof)curingagent
Lowdrying/curingtemperature
Useofcoatingbeyondpotlifeorshelflife.

Prevention:Usecorrectcoatingspecificationsandmaterials.Ensuretwopackmaterialsare
correctlymixed.Followpaintsuppliersrecommendations.

Repair:Removedefectivecoating.Abrade,cleanandrecoat.

UndercuredCoating
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Description:Acoatingthatissoftortackyandeasilydeformed.

ProbableCauses:Insufficientdrying/curingtime,curinginadverseenvironmentalconditions,
poormixingof2packcoatings.

Prevention:Ensurethatthemanufacturerstechnicaldatasheetisfollowedandthatthecoatingis
fullycuredbeforebeingplacedinservice.

Repair:Removecoatingfromthedamagedareabyabrasionandrecoat.Largeareasmay
requireblastcleaning.

Undercutting
Description:Visualcorrosionbeneathapaintfilmoftencalledcreep.Corrosiontravelsbeneath
thepaintfilmandliftsthepaintfromthesubstrate.Severecasescanshowasblistering,flaking,
cracksandexposedrust.

ProbableCauses:Applicationofpainttocorrodedsubstrate.Rustcreepfromareasof
mechanicaldamageandmissingprimercoat.Canbefoundinareasofpoordesignoraccess
whereinadequatepreparationandcoatingthicknesswasapplied.Couldalsobeduetolackof
maintenance.

Prevention:Useadequatecoatingspecificationsandmaintenanceprocedures.Applyasuitably
formulatedprimer.

Repair:Spotrepairlocalisedareas.Cleanareasbacktoasoundsubstrateandapplysuitable
repaircoatingtomanufacturersrecommendations.

WaterSpotting
Description:Thespottyappearanceofthepaintfilmcausedbydropsofwateronthesurfaceand
whichremainsafterthewaterhasevaporated.Theeffectmayormaynotbepermanent.

ProbableCauses:Themarksformedbyraindropsfallingonawetpaintfilmarepronetoleaving
permanentmarksafterevaporationwhereasraindropsfallingonafreshlydriedbuthardsurface
aremorelikelytobeabletoberubbedoffalthoughwithepoxycoatingsitmaybemoredifficult.

Prevention:Donotapplypaintwhenrainisforecast.

Repair:Wherethemarksarejustonthesurfacethesemaybewashedoffbutwherethereis
crateringorpermanentdamagetothepaintfilm,abradethesurfaceandrecoat.

Wrinkling
Description:Thedevelopmentofwrinklesinthepaintfilmduringdrying.

ProbableCauses:Usuallyduetotheinitialformationofasurfaceskinwithsolventbasedpaints.
Canarisefromovercoatingbeforethepreviouscoathasadequatelyhardened.Overthickness
particularlywithalkydcoatings.

Prevention:Usecorrectcoatingspecificationandmaterialsandensureadequatemixing,
applicationandcuringbyfollowingthepaintsuppliersrecommendations.

Repair:Removedefectivecoatings.Abrade,cleanandrecoat.

ZincSalts
Description:Theformationofzincsaltsonazincrichcoatingoronagalvanisedsurfaceduring
weathering.

ProbableCauses:Excessiveperiodofweatheringorexposuretoanaggressiveenvironment
beforeovercoating.Coatingapplicationoverzincsaltscanleadtoprematurefailure.Zincsilicate
tankcoatingsexhibitsaltformationinservicebutisnotconsideredaproblem.

Prevention:Reducetheweatheringperiod,protectfromanaggressiveenvironmentorapplyan
appropriateprotectivecoatingsystem.

Weusecookiestotrackanonymousvisitoractivity,helpingusto
Repair:Freshwaterwashthesurfacetoremovealltracesofzinccorrosionproducts.Sweepblast
orabrade,cleanandapplyasuitablecoatingsystem. OK.Don'tshowthismessageagain.
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