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首页 ASTM G42 – 96 R03

ASTM G42 – 96 R03.pdf

ASTM G42 – 96 R03

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2013-12-26 0人阅读 举报 0 0 暂无简介

简介:本文档为《ASTM G42 – 96 R03pdf》,可适用于工程科技领域

Designation:G–(Reapproved)StandardTestMethodforCathodicDisbondingofPipelineCoatingsSubjectedtoElevatedTemperaturesThisstandardisissuedunderthefixeddesignationGthenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevisionAnumberinparenthesesindicatestheyearoflastreapprovalAsuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapprovalScopeThistestmethoddescribesanacceleratedprocedurefordeterminingcomparativecharacteristicsofinsulatingcoatingsystemsappliedtosteelpipeexteriorforthepurposeofpreventingormitigatingcorrosionthatmayoccurinundergroundservicewherethepipewillbeexposedtohightemperaturesandisundercathodicprotectionThistestmethodisintendedforusewithsamplesofcoatedpipetakenfromcommercialproductionandisapplicabletosuchsampleswhenthecoatingischaracterizedbyfunctionasanelectricalbarrierThistestmethodisintendedfortestingcoatingssubmergedorimmersedinthetestsolutionatelevatedtemperatureWhenitisimpracticaltosubmergeorimmersethetestspecimen,TestMethodGmaybeconsideredwherethetestcelliscementedtothesurfaceofthecoatedpipespecimenIfroomtemperaturesarerequired,seeTestMethodsGIfaspecifictestmethodisrequiredwithnooptions,seeTestMethodGThevaluesstatedinSIunitstothreesignificantdecimalsaretoberegardedasthestandardThevaluesgiveninparenthesesareforinformationonlyThisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuseItistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouseReferencedDocumentsASTMStandards:GTestMethodsforCathodicDisbondingofPipelineCoatingsGTestMethodforNondestructiveMeasurementofFilmThicknessofPipelineCoatingsonSteelGTestMethodforSpecificCathodicDisbondingofPipelineCoatingsGTestMethodforCathodicDisbondmentTestofPipelineCoatings(AttachedCellMethod)SummaryofTestMethodThistestmethodsubjectsthecoatingonthetestspecimentoelectricalstressinahighlyconductiveelectrolyteThecoatingisartificiallyperforatedbeforestartingthetestTheelectricalstressisproducedbyconnectingthetestspecimentothenegativeterminalofasourceofdirectcurrentandbyconnectingananodetothepositiveterminalElectricalinstrumentationisprovidedformeasuringthecurrentflowinginthecellTheelectricalpotentialisalsomeasuredandthespecimenisphysicallyexaminedatintervalsduringthetestperiodanduponconclusionofthetestThecathodicstressisappliedunderconditionsofaconstantelevatedtemperatureSignificanceandUseDamagetopipecoatingisalmostunavoidableduringtransportationandconstructionBreaksorholidaysinpipecoatingsmayexposethepipetopossiblecorrosionsince,afterapipehasbeeninstalledunderground,thesurroundingearthwillbemoisturebearingandwillconstituteaneffectiveelectrolyteAppliedcathodicprotectionpotentialsmaycauselooseningofthecoating,beginningatholidayedgesSpontaneousholidaysmayalsobecausedbysuchpotentialsThistestmethodprovidesacceleratedconditionsforcathodicdisbondmenttooccurandprovidesameasureofresistanceofcoatingstothistypeofactionTheeffectsofthetestaretobeevaluatedbyphysicalexaminationsandmonitoringthecurrentdrawnbythetestspecimenUsuallythereisnocorrelationbetweenthetwomethodsofevaluation,butbothmethodsaresignificantPhysicalexaminationconsistsofassessingtheeffectivecontactofthecoatingwiththemetalsurfaceintermsofobserveddifferencesintherelativeadhesivebondItisusuallyfoundthatthecathodicallydisbondedareapropagatesfromanareawhereadhesioniszerotoanareawhereadhesionreachestheoriginallevelAnintermediatezoneofdecreasedadhesionmayalsobepresentThistestmethodisunderthejurisdictionofASTMCommitteeDonPaintandRelatedCoatings,Materials,andApplicationsandisthedirectresponsibilityofSubcommitteeDonDurabilityofPipelineCoatingandLiningsCurrenteditionapprovedDec,PublishedDecemberOriginallyapprovedinLastpreviouseditionapprovedinasG–ForreferencedASTMstandards,visittheASTMwebsite,wwwastmorg,orcontactASTMCustomerServiceatserviceastmorgForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsiteCopyright©ASTMInternational,BarrHarborDrive,POBoxC,WestConshohocken,PA,UnitedStatesAssumptionsassociatedwithtestresultsinclude:Maximumadhesion,orbond,isfoundinthecoatingthatwasnotimmersedinthetestliquid,andDecreasedadhesionintheimmersedtestareaistheresultofcathodicdisbondmentAbilitytoresistdisbondmentisadesiredqualityonacomparativebasis,butdisbondmentinthistestmethodisnotnecessarilyanadverseindicationofcoatingperformanceThevirtueofthistestmethodisthatalldielectrictypecoatingsnowincommonusewilldisbondtosomedegree,thusprovidingameansofcomparingonecoatingtoanotherThecurrentdensityappearinginthistestmethodismuchgreaterthanthatusuallyrequiredforcathodicprotectioninnaturalenvironmentsThatanyrelativelylesserbondedareawascausedbyelectricalstressingincombinationwiththeelevatedandordepressedtemperatureandwasnotattributabletoananomalyintheapplicationprocessAbilitytoresistdisbondmentisadesiredqualityonacomparativebasis,butmostinsulatingmaterialswilldisbondtosomeextentundertheacceleratedconditionsofthistestBondstrengthismoreimportantforproperfunctioningofsomecoatingsthanothersandthesamemeasureddisbondmentfortwodifferentcoatingsystemsmaynotrepresentequivalentlossofcorrosionprotectionTheamountofcurrentflowinginthetestcellmaybearelativeindicatoroftheextentofareasrequiringprotectionagainstcorrosionhowever,thecurrentdensityappearinginthistestismuchgreaterthanthatusuallyrequiredforcathodicprotectioninnatural,inlandsoilenvironmentsTestvoltageshigherthanthoserecommendedmayresultintheformationofchlorinegasThesubsequentchemicaleffectsonthecoatingcouldcastdoubtontheinterpretationofthetestresultsApparatusTestVesselAsuitablenonreactivevesselshallbeused,capableofwithstandinginternalheatingatnotlessthan°CandsuitableforcontinuouscirculationoftheelectrolyteAL(gal)cylindricalglassvesselhasbeenfoundsuitable,havinganapproximatediameterofmm(in)andadepthofmmAflatbottomisrequiredforoperationofamagneticstirringrodAnalternatemeansofheatingthetestsamplecanbeprovidedbyinternallyheatingThepipesamplemaybefilledwithasuitableheattransfermaterial(oil,steelshot,etc)AthermocoupleorthermometerandheatercanbeimmersedintheheattransfermediumtoeffectivelycontrolthetemperatureofthesampleDimensionsofthevesselshallpermitthefollowingrequirements:Testspecimensshallbesuspendedverticallyinthevesselwithatleastmm(in)clearancefromthebottomTestspecimensshallbeseparatedbynotlessthanmm(⁄in),andaverticallysuspendedanodecanbeplacedatanequaldistancefromeachspecimennotlessthantheseparationdistanceTestspecimensshallbeseparatedfromanywallofthevesselbynotlessthanmm(⁄in)DepthofelectrolyteshallpermitthetestlengthofthespecimentobeimmersedasrequiredinThereferenceelectrodemaybeplacedanywhereinthevessel,provideditisseparatedfromthespecimenandfromtheanodebynotlessthanmm(⁄in)AnodeTheanodeshallbeprovidedwithafactorysealed,insulatedcopperwireleadConnectorsWiringfromanodetotestspecimenshallbecmil(gageAwg),minimum,insulatedcopperAttachmenttothetestspecimenshallbebysolderingorbrazingtothenonimmersedend,andtheplaceofattachmentshallbecoatedwithaninsulatingmaterialAjunctionintheconnectingwireispermitted,providedthatitismadebymeansofaboltedpairofterminallugssolderedormechanicallycrimpedtocleanwireendsHolidayToolsHolidaysshallbemadewithconventionaldrillsoftherequireddiameterForuseinpreparingsmalldiameterpipespecimenssuchasmm(⁄in)nominaldiameterpipe,theuseofadrillmodifiedbysubstantiallygrindingawaythesharpconepointhasbeenfoundeffectiveinpreventingperforationofthemetalwallofthepipeAsharppointedknifewithasafehandleisrequiredforuseinmakingphysicalexaminationsMultimeters:Multimeter,fordirectcurrent,havinganinternalresistanceofnotlessthanMVandhavingarangefromtoVformeasuringpotentialtothereferenceelectrodeMultimeter,fordirectcurrent,havinganinternalresistanceofnotlessthanMVandcapableofmeasuringaslowasµVpotentialdropacrossashuntinthetestcellcircuitMultimeter,forinitialtestingofapparentcoatingresistanceReferenceElectrodeSaturatedCuCuSOelectrodehavingapotentialof−VwithrespecttothestandardhydrogenelectrodeshallbethestandardofreferenceinthesetestmethodsOtherelectrodesmaybeusedbutmeasurementsthusobtainedshallbeconvertedtotheCuCuSOreferenceforreportingbymakingthepropercorrectionNOTEAsaturatedCuCuSOelectrodereading−Vat°Cwillread−Vat°C,ascaleincreaseofVAsaturatedcalomelelectrodeat°CisconvertedtoCuCuSObyadding−VtotheobservedreadingIfthesaturatedcalomelelectrodereads−Vat°C,itwillread−Vat°C,ascaleincreaseofVItfollowsthatasaturatedcalomelelectrodereadingof−Vat°CisequaltoasaturatedCuCuSOreadingof−Vat°CAnormalcalomelelectrodeat°CisconvertedtoCuCuSObysubtracting−VfromtheobservedreadingSincethepotentialchangeduetoanincreasefrom°Cto°Cisnegligible,itfollowsthatanormalcalomelelectrodereading−Vat°CisequaltoasaturatedCuCuSOreadingof−Vat°CThermometers,two,mercuryfilledtype,accurateto°COneshallbeofthefullimmersiontypeformeasuringtemperaturenearthebottomofthevessel,andasecondDuriron,amaterialfoundsuitableforthispurposeisavailablefromDurironCo,Inc,Dayton,OHG–()thermometershallbeofthepartialimmersiontypeformeasuringtemperaturenearthetopofthevesselCombinationHeaterPlate,withbuiltinmagneticstirrer,orequivalent,shallbeusedforheatingandstirringtheelectrolyteTheheatershallbeadjustabletoproduceandcontrolatemperatureof°CinthetestvesselDirectCurrentRectifier,capableofsupplyingconstantcurrentatavoltageofV,asmeasuredbetweenthespecimenandreferencecellThicknessGage,formeasuringcoatingthicknessinaccordancewithTestMethodGPrecisionResistor,V,W(min),tobeusedinthetestcellcircuitasashuntforcurrentCarbonorStainlessSteelElectrode,usedtemporarilywiththevoltohmmetertodetermineapparentinitialholidaystatusofthetestspecimenAdditionalConnectingWires,cmil(gageAwg),minimum,insulatedcopperBrassStuds,usedataterminalboard,togetherwithalligatorclipsorknifeswitches,formakingandbreakingcircuitsAlligatorclipsshallnotbeusedtoconnecttheelectrodesorspecimensatthetoplocationoftestcellsReagentsandMaterialsTheelectrolyteshallconsistofpotabletapwaterorhigherpuritywater(distilledordemineralizedwaterissatisfactory)withtheadditionofweightofeachofthefollowingtechnicalgradesalts,calculatedonananhydrousbasis:sodiumchloride,sodiumsulfate,andsodiumcarbonateNOTETheresultingsolutionhasapHoforhigherandaresistivityoftoV·cmatroomtemperatureMaterialsforsealingtheendsofcoatedpipespecimensmayconsistofbituminousproducts,wax,epoxy,orothermaterials,includingmoldedelastomericorplasticendcaps,capableofwithstandingthetesttemperaturePlywoodhasbeenfoundsuitablefortheconstructionofnonconductivetestvesselcoversandforthesupportthroughaperturesoftestspecimensandelectrodesWooddowelsintroducedthroughholesinthetopendsoftestspecimenshavebeenfoundsuitableforsuspendingtestspecimensfromthevesselcoverTestSpecimenThetestspecimenshallbearepresentativepieceofproductioncoatedpipeOneendshallbeplugged,sealed,orcappedOneholidayshallbemadeinthemiddleoftheimmersedlengthbydrillingaradialholethroughthecoatingsothattheangularconepointofthedrillwillfullyenterthesteelwherethecylindricalportionofthedrillmeetsthesteelsurfaceThedrilldiametershallbenotlessthanthreetimesthecoatingthickness,butitshallneverbelessthanmm(⁄in)indiameterThesteelwallofthepipeshallnotbeperforatedWithsmalldiameterpipes,wherethereisdangerofperforatingthepipe,theholidayshallbestartedwithastandard°conepointandfinishedwithadrillthathashadasubstantialportionoftheconepointgroundawayNOTEBeforemakingtheholiday,seeTheendofthepipewhichwillprotrudeabovetheimmersionlineshallbeprovidedwithsuitablesupportingmeansandaseparatewireconnectionforelectricalpurposes,soldered,orbrazedtothepipeTheprotrudingend,includinghangerandwireconnections,shallbeprotectedandsealedwithaninsulatingcoatingmaterialNOTEFormultiplespecimensinthesametestvessel,seeFig,forcircuitdiagramusingvoltagedividersFIGTestSetUpforCathodicDisbondingTestatElevatedTemperatureG–()ThespecimentestareashallconsistoftheareabetweentheedgeofthebottomendsealandtheimmersionlineThebottomendsealareashallnotbeconsideredpartoftheareatestedCoatedspecimensofanysuitablediameterandlengthofpipemaybeused,buttheimmersedareashallbenotlessthanmm(in)Anareaofmm(ft)hasbeenfoundpreferablewhenconvenientThecontinuityofthecoatingandefficiencyoftheendsealshallbetestedbeforemakingartificialholidaysasfollows:ImmersethetestspecimenandacarbonorstainlesssteelelectrodeintheelectrolyteConnectoneterminaloftheohmmetertothetestspecimenandtheotherterminaltothecarbonorstainlesssteelelectrodeMeasuretheapparentresistanceinohms,makingtwodeterminations:onewiththespecimenconnectedtothepositiveterminaloftheohmmeter,andonewiththespecimenconnectedtothenegativeterminalThelowestofthetworeadingsshouldbenotlessthanMV,however,thetestmaybeconductedwithalowreadinglessthanMV,providedthattheconditionistakenintoaccountinevaluatingresultsProcedureImmersethetestspecimenintheelectrolyteandconnectittotheanodeasshowninFigAdjusttherectifierorvoltagedividersothatthepotentialbetweenspecimenandreferencecellis−Vat°C(−Vat°C)(seeFig)TheholidaymaybepositionedfacingtheanodeorfacingawayfromtheanodeasdescribedinTestMethodsGSpacetheanodewithrespecttotestspecimensasrequiredinMarkthecorrectimmersionlevelontheexteriorofthetestvesselandmaintainbydailyadditionsofpreheated,distilled,ordemineralizedwaterasrequiredWhenusingtheelectrolyteheatingmethodsthetemperatureoftheelectolytesurfacetobottomshallbenotlessthan°CTheelectrolyteshallbecontinuouslycirculatedbymeansofthestirringapparatusorequivalentThemaximumtemperatureshallbeattainedhafterstartingtheheaterandimmersingthespecimenNOTEThroughoutthetestperiod,ejectedsealantorsaltdeposits,orboth,mayformnear,orpartiallyobstructtheintentionalcoatingholidaydescribedinNoattemptshallbemadetocleartheholidaywhilethetestisinprogressElectricalMonitoringSchedule:ElectricalmeasurementsshallbemadeonthestartupdayandoneachnormalworkingdaythereafterforthedurationofthetestAmaximumofthreeconsecutivenonworkingdaysshallbeprecededbyatleasttwoworkingdaysonenonworkingdayortwoconsecutivenonworkingdaysshallbeprecededbyatleastoneworkingday,exceptatstartupandterminationwhenthreeandtwoworkingdaysarerequired,respectivelyElectricalmeasurementscharacterizingthestartofthetestaredefinedastheaverageofmeasurementstakenonthesecondandthirddaysafterimmersionElectricalmeasurementscharacterizingintermediateandterminaltimespansshallbetakenontwosuccessivedayspriortoandincludingthetargetdateElectricalmeasurementsandadjustmentsmadeeachnormalworkingday:FIGCircuitDiagramforCathodicDisbondingTestG–()MeasureE,thestresspotentialinvoltsbetweenthetestspecimenandthereferenceelectrode,withoutdisconnectingtheenergizedanodeorspecimenfromthecircuitUsethehighresistancevoltmeterdescribedinThestresspotential,E,shouldmeasure−Vat°C(−Vat°C)ifitdoesnot,adjusttherectifierorvoltagedivideraccordinglyAfterEhasbeenmeasuredandadjusted,ifnecessary,measureI,thecurrentdemandinamperes,bydeterminingthepotentialdropacrosstheVprecisionresistorpermanentlyinstalledinthetestcellcircuitwiththehighresistancevoltmeterdescribedinThevoltagereadingwillbenumericallyequaltoamperesNOTEAnalternativemethodofmeasuringcurrentdemandutilizesazeroresistanceammeterInthismethod,thewireconnectionbetweenthetestspecimenandanodeistemporarilybrokenandazeroresistanceammetertemporarilyinterposedbetweenthespecimenandtheanodeReconnectthespecimentotheanodewiththeconnectorwireassoonasthismeasurementiscompletedMeasureE,thepolarizedpotential,involts,usingthehighresistancevoltmeterdescribedinconnectedbetweenthetestspecimenandthereferenceelectrodeasfollows:DisconnecttheanodefromthetestspecimenwhilecloselyobservingthehighresistancevoltmeterAstheinstrumentpointerfalls,itwilldwellsignificantlyatthepolarizedpotentialbeforerecordingfurtherThedwellpointisEStandarddurationofthetestperiodshallbedays(h)intheenergizedtestvesselincludingwarmupandcooldowntimes,unlesslongertestperiodsarespecifiedAphysicalexaminationshallbeperformedimmediatelyuponterminationofthetestperiodasfollow

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