【astm標(biāo)準(zhǔn)】g 3 - 14

1、Designation:G3?14StardPracticefConventionsApplicabletoElectrochemicalMeasurementsinCrosionTesting1ThisstardisissuedunderthefixeddesignationG3thenumberimmediatelyfollowingthedesignationindicatestheyearofiginaladoptioninth

2、ecaseofrevisiontheyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperepsilon()indicatesaneditialchangesincethelastrevisionreapproval.1.Scope1.1Thispracticecoversconventionsfreptingdisplayingele

3、ctrochemicalcrosiondata.Conventionsfpotentialcurrentdensityelectrochemicalimpedanceadmittanceaswellasconventionsfgraphicalpresentationofsuchdataareincluded.1.2ThevaluesstatedinSIunitsaretoberegardedasstard.Nootherunitsof

4、measurementareincludedinthisstard.Seealso7.4.1.3Thisstarddoesnotpurpttoaddressallofthesafetyconcernsifanyassociatedwithitsuse.Itistheresponsibilityoftheuserofthisstardtoestablishappropriatesafetyhealthpracticesdeterminet

5、heapplicabilityofregulatylimitationspritouse.2.ReferencedDocuments2.1ASTMStards:2IEEEASTMSI10StardfUseoftheInternationalSystemofUnits(SI)(theModernMetricSystem)3.SignificanceUse3.1Thispracticeprovidesguidancefreptingdisp

6、layingplottingelectrochemicalcrosiondataincludesrecommendationsonsignsconventions.Useofthispracticewillresultinthereptingofelectrochemicalcrosiondatainastardfmatfacilitatingcomparisonbetweendatadevelopedatdifferentlabati

7、esatdifferenttimes.Therecommendationsoutlinedinthisstardmaybeutilizedwhenrecdingreptingcrosiondataobtainedfromelectrochemicaltestssuchaspotentiostaticpotentiodynamicpolarizationpolarizationresistanceelectrochemicalimpeda

8、nceadmittancemeasurementsgalvaniccrosionopencircuitpotentialmeasurements.4.SignConventionfElectrodePotential4.1TheStockholmsigninvariantconventionisrecommendedfuseinreptingtheresultsofspecimenpotentialmeasurementsincrosi

9、ontesting.Inthisconventionthepositivedirectionofelectrodepotentialimpliesanincreasinglyoxidizingconditionattheelectrodeinquestion.Thepositivedirectionhasalsobeendenotedasthenobledirectionbecausethecrosionpotentialsofmost

10、noblemetalssuchasgoldaremepositivethanthenonpassivebasemetals.Ontheotherhthenegativedirectionoftencalledtheactivedirectionisassociatedwithreductionconsequentlythecrosionpotentialsofactivemetalssuchasmagnesium.Thisconvent

11、ionwasadoptedunanimouslybythe1953InternationalUnionofPureAppliedChemistryasthestardfelectrodepotential(1).34.2InthecontextofaspecimenelectrodeofunknownpotentialinanaqueouselectrolyteconsiderthecircuitshowninFig.1witharef

12、erenceelectrodeconnectedtothegroundterminalofanelectrometer.Iftheelectrometerreadsonscalewhenthepolarityswitchisnegativethespecimenelectrodepotentialisnegative(relativetothereferenceelectrode).Converselyiftheelectrometer

13、readsonscalewhenpolarityispositivethespecimenpotentialispositive.Ontheotherhifthespecimenelectrodeisconnectedtothegroundterminalthepotentialwillbepositiveifthemeterisonscalewhenthepolarityswitchisnegativeviceversa.NOTE1—

14、Incaseswherethepolarityofameasuringinstrumentisindoubtasimpleverificationtestcanbeperfmedasfollows:connectthemeasuringinstrumenttoadrycellwiththeleadpreviouslyonthereferenceelectrodetothenegativebatteryterminaltheleadpre

15、viouslyonthespecimenelectrodetothepositivebatteryterminal.Settherangeswitchtoaccommodatethedrycellvoltage.Themeterdeflectionwillnowshowthedirectionofpositivepotential.Alsothecrosionpotentialofmagnesiumzincshouldbenegativ

16、eina1NNaClsolutionifmeasuredagainstasaturatedstardcalomelelectrode(SCE).1ThispracticeisunderthejurisdictionofASTMCommitteeG01onCrosionofMetalsisthedirectresponsibilityofSubcommitteeG01.11onElectrochemicalMeasurementsinCr

17、osionTesting.CurrenteditionapprovedDec.152014.PublishedDecember2014.iginallyapprovedin1968.Lastpreviouseditionapprovedin2013asG3–13.DOI:10.1520G000314.2FreferencedASTMstardsvisittheASTMwebsitewww.astm.gcontactASTMCustome

18、rServiceat.FAnnualBookofASTMStardsvolumeinfmationrefertothestard’sDocumentSummarypageontheASTMwebsite.3Theboldfacenumbersinparenthesesrefertoalistofreferencesattheendofthisstard.Copyright?ASTMInternational100BarrHarbDriv

19、ePOBoxC700WestConshohockenPA194282959.UnitedStates1typesofelectrodebehavicanbeplottedinaccdancewiththeproposedconventions.8.ConventionsfDisplayingElectrochemicalImpedanceData8.1Threegraphicalfmatsincommonusefreptingelect

20、rochemicalimpedancedataaretheNyquistBodeAdmittancefmats.ThesefmatsarediscussedfasimpleelectrodesystemmodelledbyanequivalentelectricalcircuitasshowninFig.7.Intheconventionutilizedtheimpedanceisdefinedas:Z5Z1jZ“(3)where:Z=

21、realinphasecomponentofimpedanceZ“=theimaginaryoutofphasecomponentofimpedancej2=?1.Theimpedancemagnitudemodulusisdefinedas|Z|2=(Z)2(Z“).FtheequivalentelectricalcircuitshowninFig.7theimaginarycomponentofimpedanceZ“5212πfC(

22、4)where:f=frequencyincyclespersecond(hertzHzwhereoneHzisequalto2πradianssw=2πfwheretheunitsfwareradianss)C=capacitanceinfarads.Thephaseangleθisdefinedas:θ5arctan~Z“Z!(5)TheadmittanceYisdefinedas1Z5Y5Y1jY“(6)where:FIG.2Hy