Designation:G67−13StandardTestMethodforDeterminingtheSusceptibilitytoIntergranularCorrosionof5XXXSeriesAluminumAlloysbyMassLossAfterExposuretoNitricAcid(NAMLTTest)1ThisstandardisissuedunderthefixeddesignationG67;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethoddescribesaprocedureforconstantimmersionintergranularcorrosiontestingof5XXXseriesaluminumalloys.1.2Thistestmethodisapplicableonlytowroughtproducts.1.3Thistestmethodcoverstypeofspecimen,specimenpreparation,testenvironment,andmethodofexposure.1.4ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesgiveninparenthesesareforinformationonly.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D1193SpecificationforReagentWaterG1PracticeforPreparing,Cleaning,andEvaluatingCorro-sionTestSpecimens3.SummaryofTestMethod3.1Thistestmethodconsistsofimmersingtestspecimensinconcentratednitricacidat30°C(86°F)for24handdeterminingthemasslossperunitareaasameasureofsusceptibilitytointergranularcorrosion.4.SignificanceandUse4.1ThistestmethodprovidesaquantitativemeasureofthesusceptibilitytointergranularcorrosionofAl-MgandAl-Mg-Mnalloys.Thenitricaciddissolvesasecondphase,analuminum-magnesiumintermetalliccompound(βAl-Mg),inpreferencetothesolidsolutionofmagnesiuminthealuminummatrix.Whenthiscompoundisprecipitatedinarelativelycontinuousnetworkalonggrainboundaries,theeffectofthepreferentialattackistocorrodearoundthegrains,causingthemtofallawayfromthespecimens.Suchdroppingoutofthegrainscausesrelativelylargemasslossesoftheorderof25to75mg/cm2(160to480mg/in2),whereas,samplesofin...
