ASTM-F746

Designation:F746−04(Reapproved2009)´1StandardTestMethodforPittingorCreviceCorrosionofMetallicSurgicalImplantMaterials1ThisstandardisissuedunderthefixeddesignationF746;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.´1NOTE—UnitsinformationwaseditoriallycorrectedinJanuary2010.1.Scope1.1Thistestmethodcoversthedeterminationofresistancetoeitherpittingorcrevicecorrosionofmetalsandalloysfromwhichsurgicalimplantswillbeproduced.Itisamodifiedversionofanestablishedtest2andisusedasascreeningtesttoranksurgicalimplantalloysinorderoftheirresistancetolocalizedcorrosion.1.2Thistestmethodappliesonlytopassivemetalsandalloys.Nonpassivealloys(otherthannoblealloys)aresuscep-tibletogeneralcorrosionandarenotnormallysuitableforimplantuse.1.3Thistestmethodisintendedforuseasalaboratoryscreeningtestformetalsandalloyswhichundergopittingorcrevicecorrosion,orboth.1.4ThevaluesstatedineitherSIunitsorinch-poundunitsaretoberegardedseparatelyasstandard.Thevaluesstatedineachsystemmaynotbeexactequivalents;therefore,eachsystemshallbeusedindependentlyoftheother.Combiningvaluesfromthetwosystemsmayresultinnon-conformancewiththestandard.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:3D1193SpecificationforReagentWaterF86PracticeforSurfacePreparationandMarkingofMetal-licSurgicalImplantsF2129TestMethodforConductingCyclicPotentiodynamicPolarizationMeasurementstoDeterminetheCorrosionSusceptibilityofSmallImplantDevicesG3PracticeforConventionsApplicabletoElectrochemicalMeasurementsinCorrosionTestingG5ReferenceTestMethodforMakingPotentiostaticandPotentiodynamicAnodicPolarizationMeasurementsG15TerminologyRelatingtoCorrosionandCorrosionTest-ing(Withdrawn2010)43.SummaryofTestMethod3.1Acylindricalspecimenfittedwithaninerttaperedcollarisimmersedinaphosphatebufferedsalineelectrolyteat37°Cfor1htoestablishacorrosionpotential.Pitting(orcrevicecorrosion)isthenstimulatedbypotentiostaticallypolarizingthespecimentoapotentialmuchmorenoblethanthecorrosionpotential.Stimulationofpitting(orcrevicecorrosion)willbemarkedbyalargeandgenerallyincreasingpolarizingcurrent.3.2Immediatelyafterthestimulationstep,thepotentialisdecreasedasrapidlyaspossibletooneofseveralpreselectedpotentialsat,ormorenoblethan,thecorrosionpotential.Ifthealloyissusceptibletopitting(orcrevicecorrosion)atthepreselectedpotential,thepolarizingcurrentwillremainatrelativelyhighvaluesandwillfluctuateorincreasewithtime.Apost-testexaminationofthemetalspecimenestablisheswhetherlocalizedcorrosionhasoccurredbypittingoftheexposedsurfaceorbypreferentialattackatthecreviceformedbythetaperedcollar,orboth.3.3Ifthepit(orcrevice)surfacerepassivatesatthepre-selectedpotentialandlocalizedcorrosionishalted,thepolar-izingcurrentwilldroptovaluestypicalforpassivesurfacesandthecurrentwilldecreasecontinuously.Theparameterofinterest,thecriticalpotentialforpitting(orcrevicecorrosion),isdefinedasthehighest(mostnoble)pre-selectedpotentialatwhichpit(orcrevice)surfacesrepassivateafterthestimulationstep.1ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedicalandSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommitteeF04.15onMaterialTestMethods.CurrenteditionapprovedDec.1,2009.PublishedJanuary2010.Originallyapprovedin1981.Lastpreviouseditionapprovedin2004asF746–04.DOI:10.1520/F0746-04R09E01.2Syrett,B.C.,Corrosion,Vol33,1977,p.221.3ForreferencedASTMstandards,visittheASTMwebsite,@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.4Thelastapprovedversionofthishistoricalstandardisreferencedon©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959.UnitedStates1CopyrightbyASTMInt'l(allrightsreserved);4.SignificanceandUse4.1Thistestmethodisdesignedsolelyfordeterminingcomparativelaboratoryindicesofperformance.Theresultsmaybeusedforrankingalloysinorderofincreasingresistancetopittingandcrevicecorrosionunderthespecificconditionsofthismethod.Itshouldbenotedthatthemethodisintentionallydesignedtoreachconditionsthataresufficientlyseveretocausebreakdownofatleastonealloy(Type316Lstainlesssteel)currentlyconsideredacceptableforsurgicalimplantuse,andthatthosealloyswhichsufferpittingorcrevicecorrosionduringthemoresevereportionsofthetestdonotnecessarilysufferlocalizedcorrosionwhenplacedwithinthehumanbodyasasurgicalimplant.5.Apparatus5.1ThefollowingrequiredequipmentisdescribedinRef-erenceTestMethodG5:5.1.1StandardPolarizationCell,of1000cm3.5.1.2ElectrodeHolders,forauxiliaryandworkingelec-trodes.5.1.3Potentiostat,calibratedinaccordancewithReferenceTestMethodG5.5.1.4Pote