ASTM-B568-1998

Designation:B568–98(Reapproved2004)StandardTestMethodforMeasurementofCoatingThicknessbyX-RaySpectrometry1ThisstandardisissuedunderthefixeddesignationB568;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.1.Scope1.1ThistestmethodcoverstheuseofX-rayspectrometrytodeterminethicknessofmetallicandsomenonmetalliccoatings.1.2Themaximummeasurablethicknessforagivencoatingisthatthicknessbeyondwhichtheintensityofthecharacter-isticsecondaryXradiationfromthecoatingorthesubstrateisnolongersensitivetosmallchangesinthickness.1.3Thistestmethodmeasuresthemassofcoatingperunitarea,whichcanalsobeexpressedinunitsoflinearthicknessprovidedthatthedensityofthecoatingisknown.1.4Problemsofpersonnelprotectionagainstradiationgen-eratedinanX-raytubeoremanatingfromaradioisotopesourcearenotcoveredbythistestmethod.Forinformationonthisimportantaspect,referenceshouldbemadetocurrentdocumentsoftheNationalCommitteeonRadiationProtectionandMeasurement,FederalRegister,NuclearRegulatoryCom-mission,NationalInstituteofStandardsandTechnology(for-merlytheNationalBureauofStandards),andtostateandlocalcodesifsuchexist.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2E135TerminologyRelatingtoAnalyticalChemistryforMetals,Ores,andRelatedMaterials2.2InternationalStandard:ISO3497MetallicCoatings—MeasurementofCoatingThickness—X-raySpectrometricMethods3.Terminology3.1DefinitionsoftechnicaltermsusedinthistestmethodmaybefoundinTerminologyE135.4.SummaryofTestMethod4.1Excitation—Themeasurementofthethicknessofcoat-ingsbyX-rayspectrometricmethodsisbasedonthecombinedinteractionofthecoatingandsubstratewithincidentradiationofsufficientenergytocausetheemissionofsecondaryradia-tionscharacteristicoftheelementscomposingthecoatingandsubstrate.TheexcitingradiationmaybegeneratedbyanX-raytubeorbycertainradioisotopes.4.1.1ExcitationbyanX-RayTube—Suitableexcitingradia-tionwillbeproducedbyanX-raytubeifsufficientpotentialisappliedtothetube.Thisisontheorderof35to50kVformostthickness-measurementapplications.ThechiefadvantageofX-raytubeexcitationisthehighintensityprovided.4.1.2ExcitationbyaRadioisotope—Ofthemanyavailableradioisotopes,onlyafewemitgammaradiationsintheenergyrangesuitableforcoating-thicknessmeasurement.Ideally,theexcitingradiationisslightlymoreenergetic(shorterinwave-length)thanthedesiredcharacteristicXrays.Theadvantagesofradioisotopeexcitationincludemorecompactinstrumenta-tionessentiallymonochromaticradiation,andverylowback-groundintensity.ThemajordisadvantageofradioisotopeexcitationisthemuchlowerintensitiesavailableascomparedwithX-raytubesources.X-raytubestypicallyhaveintensitiesthatareseveralordersofmagnitudegreaterthanradioisotopesources.Duetothelowintensityofradioisotopes,theyareunsuitableformeasurementsonsmallareas(lessthan0.3mmindiameter).Otherdisadvantagesincludethelimitednumberofsuitableradioisotopes,theirrathershortusefullifetimes,andthepersonnelprotectionproblemsassociatedwithhigh-intensityradioactivesources.4.2Dispersion—ThesecondaryradiationresultingfromtheexposureofanelectroplatedsurfacetoXradiationusuallycontainsmanycomponentsinadditiontothosecharacteristicofthecoatingmetal(s)andthesubstrate.Itisnecessary,therefore,tohaveameansofseparatingthedesiredcompo-nentssothattheirintensitiescanbemeasured.Thiscanbe1ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallicandInorganicCoatingsandisthedirectresponsibilityofSubcommitteeB08.10onTestMethods.CurrenteditionapprovedJune1,2004.PublishedJune2004.Originallyapprovedin1972.Lastpreviouseditionapprovedin1998asB568–98.2ForreferencedASTMstandards,visittheASTMwebsite,@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.1Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.CopyrightASTMInternationalReproducedbyIHSunderlicensewithASTMNotforResaleNoreproductionornetworkingpermittedwithoutlicensefromIHS--````,`-`-`,,`,,`,`,,`---doneeitherbydiffraction(wavelengthdispersion)orbyelectronicdiscrimination(energydispersion).4.2.1WavelengthDispersion—Bymeansofasingle-crystalspectrogoniometer,wavelengthscharacteristicofeitherthecoatingorthesubstratemaybeselectedformeasurement.Publisheddataintabularformareavailablethatrelatespec-trogoniometersettingstothecharacteristicemissionsofele-mentsforeachofthecommonlyusedanalyzingcrystals.4.2.2EnergyDispersion—X-rayquantaareusuallyspeci-fiedintermsoftheirwavelengths,inangstroms(Å),ortheirequivalentenergiesinkiloelectronvolts(keV).Therelation-