Designation:C743−87(Reapproved2018)StandardTestMethodforContinuityofPorcelainEnamelCoatings1ThisstandardisissuedunderthefixeddesignationC743;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThistestprovidesameanstoevaluateaporcelainenamelcoatingforpinholes,discontinuities,andinsufficientapplicationtobetterassesstheabilityofthecoatingtoprotectthesubstrate.1.Scope1.1Porcelainenamelcoatingsareappliedtometalstoprovideprotectionfromcorrosionaswellastoenhancetheirappearance.Thistestmethodpermitstheeasydetectionofdiscontinuitiesandareasoflightcoverage,notreadilyseenbyvisualinspection,whichlimittheprotectiontothesubstrate.SomewhatsimilartestsapplicabletothethickerglasscoatingsusedforchemicalreactionvesselsarefoundinTestMethodsC536andC537.1.2ValuesstatedinSIunitsaretoberegardedasthestandard.Inch-poundunitsareprovidedforinformationonly.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.1.4Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTradeOrganizationTechnicalBarrierstoTrade(TBT)Committee.2.ReferencedDocuments2.1ASTMStandards:2C536TestMethodforContinuityofCoatingsinGlassedSteelEquipmentbyElectricalTestingC537TestMethodforReliabilityofGlassCoatingsonGlassedSteelReactionEquipmentbyHighVoltage3.Terminology3.1air-gapvoltage—voltageneededtoarcthroughadefectthatisopentoboththesurfaceoftheporcelainenamelandthemetalsubstrate.Thelengthoftheairgapisestimatedbymeasuringtheenamelthickness...
