faraday’s law applied to cleaning _ products finishing
DESCRIPTION
platingTRANSCRIPT
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FaradaysLawAppliedtoCleaningArticle:ExternalFrom:ProductsFinishingPostedon:3/18/2015
Thispaperisarepublicationofthethe2ndWilliamBlumLecture,presentedatthe47thAESAnnualConventioninLosAngelesbyDr.A.KennethGraham,1959AESScientificAchievementAwardrecipient.WhileFaraday'sLawhadlongbeenappliedtoelectrodepositionprocesses,Dr.Grahamtookitastepfurther,consideringitsusageintheelectrocleaningofvariousmetalsubstratesintermsofelectricalchargepassedduringthecleaningoperation.
by
Dr.A.KennethGraham
Recipientofthe1959AESScientificAchievementAward
EditorsNote:OriginallypublishedasA.K.Graham,AnnualTechnicalProceedingsoftheAmericanElectroplatersSociety,47,4144(1960),thisarticleisarepublicationof
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the2ndWilliamBlumLecture,presentedatthe47thAESAnnualConventioninLosAngeles,California,onJuly25,1960.AprintablePDFversionisavailablebyclickingHERE.
Introductionandbackground
WhatisFaraday'sLaw?"ThatwastheonlyquestionaskedmebytheplatingforemanoftheWelsbachCompanyin1921whenthesuperintendentintroducedmeandinquirediftheremightbeajobavailableforme.Atthetime,IhadmyBSdegreeinchemicalengineeringandtwoyearsexperienceinindustry,butrecognizedthepracticalvalueofworkingoverthetanksunderanexperiencedplater.Thesuperintendentagreedtogivemetheopportunitytoapplyforsuchajobwithoutdisclosingmybackground.Igotthejobbyansweringthequestion"WhatisFaraday'sLaw?"
AllofyouappreciatethatFaraday'stwoLawsarethebasisofallplatingand,infact,oftheentireElectrochemicalIndustry.Intheyearssincethelastwar,wehavelearnedthattheycanbeappliedwithgreatadvantagetocleaningaswellasplating.ItisabouttheirapplicationtocleaningthatIwishtospeaktoday.
Cleaningofthecommonbasismetalsforpresentdaydecorativeandprotectiveplatingapplicationshasbeendevelopedtothepointwheretheconscientiousplatercanapplytheavailableinformationanddoanacceptablejob.However,thepresentdayplatingapplicationsinotherareas,thesocalledengineeringapplications,arepresentinganeverincreasingarrayofcleaningandplatingproblems.Oneindustryrequireselectrodepositedgold,silveroralloycoatingonberylliumcopper,bronzeorbrasstapeorwire.Coatingsofbuffednickeloverbuffednickelwithorwithoutafinalchromiumcoatinghavebeenusedtoovercomecavitationfailureofdieselcylinderlinersandtoobtainimprovedcorrosionresistanceinvariousapplications.Manyvarietiesofstainlesssteelalloysmustbeadherentlyplatedwithvariousmetalstomeetspecialservicerequirements.Theextremelypassivematerials,suchasStellite,Inconel,Hastalloy,andCarballoysometimesrequireadherentplatedcoatingsforsomeapplications.Sometimesthemoreexoticmetals,suchasniobium,titanium,zirconium,uranium,berylliumandmolybdenum,requireadherentplatedcoatingsforvariousreasons.Itisreasonabletoassumethatsuchproblemswillincreaseinthefuture.
Suchengineeringplatingapplicationswillonlybesuccessfulifoneisabletodevelop
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cleaningcyclesthatwillpermitonetodepositadherentmetalcoatings.Toaccomplishthisonemustremoveoxideorothersurfacefilmsandthenkeepthebasismetalsurfaceactivateduntiltheplatedcoatingcanbeapplied.Thechemistryofsomeofthebasismetalsinvolvedrenderthisextremelydifficult.Thereismuchyettobelearnedaboutthesematters.
Theconventionalapproachtosolvingsuchaproblemistofirstremoveorganicsoilsbysuitabledegreasingmeans,includinganelectrocleaningtreatment.Whetherthelattershouldbeanodicorcathodicisnotalwaysclear.Inanyevent,thecommonlyrecommendedconditionsforaproprietarycleanersuchasconcentration,temperature,currentdensityandtime,areusuallyemployed.Someacidtreatmentwithorwithouttheuseofcurrentisthenchosentoetchandactivatethesurfaceandthecommonlyrecommendedconditionsofbathcomposition,concentration,temperature,timeandcurrent,ifany,arepreciselyfollowed.Insomecases,ifallowable,theWood'stypeofnickelchloridestrikeisfinallyusedundertheconditionsrecommended.Iftheseproceduresthendonotgivethedesiredresults,wereallydohaveaproblem.
Undersuchcircumstances,IhavefounditmosthelpfultosimplyapplyFaraday'sLawstotheelectrolytictreatments.IthereforetrustyouwillbearwithmeifIbrieflydiscusstheseLawsinanelementaryfashionasappliedtocleaning.
AccordingtoFaraday'sfirstLaw,theamountofchemicalchangeproducedbyanelectriccurrentflowingthroughanelectrolyteisproportionaltothequantityofelectricity.Thequantityofelectricityistheproductofthecurrentflowingtimesthetime.Theunitofquantity,acoulomb,isoneampereflowingforonesecond.Tenamperesflowingforsixsecondswillcausethesamechemicalchangeasoneampereforsixtyseconds,bothbeingthesamequantityofelectricity,60coulombsoroneampereminute.Ineithercase,thesameamountofhydrogenwillbeliberatedatametalsurfaceincathodiccleaning.Ifonedoublesthequantityofelectricity,theamountofhydrogenliberatedalsowillbedoubled.Whateverbenefitmaybederivedfromtheliberationofhydrogenincathodiccleaningmaythereforebevariedbyapplyingthisconcept.
AccordingtoFaraday'ssecondLaw,theamountsofdifferentsubstancesliberatedbyagivenquantityofelectricityareproportionaltotheirchemicalequivalentweights.Statedanotherway,96,500coulombsoroneFaradayofelectricitywillliberateoneequivalentweightoronegramofhydrogenatthecathodeandoneequivalentweightoreightgramsofoxygenattheanodeinalkalineelectrocleaning.Therefore,theeffectoftheoxygenliberatedinanodiccleaning,whetherbeneficialorotherwise,canalsobevaried
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quantitativelybyapplyingthisLaw.
AccordingtoAvogadro,agrammolecularweightofanygasoccupiesthesamevolumeatthesametemperatureandpressure.Sincetheequivalentorcombiningweightofhydrogenisonehalfitsmolecularweight,butthatofoxygenisonlyonefourthitsmolecularweight,thenthevolumeofhydrogenliberatedatthecathodeinalkalineelectrocleaningistwicethevolumeofoxygenliberatedattheanode.ThusthiswellknownvolumerelationshipfollowsdirectlyfromFaraday'sLaws.Also,thegreatervolumeofhydrogenliberatedatthecathodeledtothepreferreduseofcathodicelectrocleaningintheearlydays.
Inmanycasesthescrubbingactionofthevolumeofgasliberatedatthesurfaceofthemetalinalkalineelectrocleaningisofsecondaryimportancetothenatureofrelatedchemicalreactionsandthisdependsuponthereactionsofhydrogenandoxygenattheelectrodesurfaces.Inouropinion,theresultingadhesionoftheelectrodepositedmetalcoatingisthemostimportantfactor,bothasanindicationofaproperlycleanedsurfaceandasameansofinsuringqualityoftheplatedcoating.Experiencehasshownthatgoodadhesionisfavoredbyanodiccleaningofthecommonferrousmetals.Cathodiccleaningisusuallypreferredfornickel.Copperorzinccanbecleanedeitherwayforgoodadhesion,butanodiccleaningismostcommonlyusedtoavoiddepositionoffilms.Leadiscathodicallycleanedtoavoidetchingandstaining.
Thecleaningofmanymetalspriortoplatingaspracticedtodayfrequentlyinvolvesvariouspretreatmentsincombinationwithbothelectrolytealkalineandacidsteps.Theseelectrolytictreatmentsareusuallylimitedtonotovertwominutesandoftentooneminuteorless.Thetanksizesandconveyorchainspeedfrequentlydeterminesthis.Also,thecurrentdensityiseitherlimitedtothatobtainableatthevoltageofthecurrentsourceavailableorispurposelyrestrictedbecauseofthesensitivityofaparticularmetalsurfacewithrespecttoetchingorstaining.Thisisespeciallytruefordecorativebrightplatedfinishes.Thusthequantityofelectricity,theproductofthetimemultipliedbytheamperesflowing,istherebylimitedandtheapplicationofFaraday'sLaws,inanyrealsense,hasbeendisregardedasfarascleaningisconcerned.
Ofcoursethisisnotsowithplating.OneFaradayor96,500coulombsofelectricitywilldepositonechemicalequivalentorcombiningweightofanymetalat100percentcathodeefficiency.WeroutinelyrefertotheTableofElectrochemicalEquivalentsandRelatedDatatofindtheampereminutesrequiredtodepositanymetaltoacoatingthicknessofonemilpersquarefoot.Fromthiswedeterminetheplatingtimerequired
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atagivencurrentdensitytodepositanythicknessofmetalorviceversa.Westilldesignandcontrolourplatingoperationstoobtainagivenplatingtimeatacontrolledaveragecurrentdensitytoobtainacontrolledaverageweightofmetalcoating.Wealsomakeallowancefortheefficiencyoftheplatingprocessandforvariationsincurrentandmetaldistributionwiththedesignofthepartbeingplated.AllthisisstrictlyinaccordancewithFaraday'sLaws.
WealsoknowthatFaraday'sLawsapplytotheperformanceofsolubleanodesinplatingandthatthemetalplatedoutatthecathodeissubstantiallyallsuppliedbymetaldissolvingattheanodeinproperlycontrolledprocesses.
ToapplyFaraday'sLawstocleaningismuchmoredifficultandonemightask,"Whybother?"Itismoredifficultbecauseweareobligedtoremovesomanydifferenttypesofsoil,andthetermsoilisusedhereinthebroadestsense.Thesurfacechemistryofthebasismetalitselfcannotbedefined.Asmanyofyouwellknowwhochromiumplatenickel,thesurfacechemistryofanickelcoatingimmediatelyafterplatingisdifferentthanonethathasjustbeenbuffedandbothwillbedifferentafterexposuretoairfor24hours.Thesurfacechemistryalsovarieswitheachmetalanditsmetallurgicalhistory.Onethereforecannotdeterminethechemicalequivalentweightofthecombinationofsoils,oxidesandmetalsurfacefilmsandrelateittoagivenquantityofelectricityincleaning.OuronlyrecourseistoapplythequantitativeconceptsofFaradayblindly.Increasingthecurrentdensityand/orthetimewillquantitativelyincreasethehydrogenandoxygenliberatedandthechemicalreactionsresultingatbothanodeandcathodeinelectrocleaningtreatments,eventhoughthereactionsareundefined.Bysodoingwecanaccomplishresultsincleaningandplatingthatcanbeguaranteedandnotlefttochance.Thisisespeciallytruewithrespecttothesocalledengineeringapplications,manyofwhichrequireplatinguponthemoredifficultorunusualbasismetals.
Mr.F.W.Stockton,formerlyoftheStandardSteelSpringCo.,wasthefirst,toourknowledge,toemphasizetheimportanceofFaraday'sLawsinelectrocleaning.Heobservedthatcathodiccleaningofsteelpriortonickelplatinggaveverypooradhesion,comparedtoanodiccleaning.Hethenshowed,ifcathodiccleaningwasfirstused,theadverseeffectofthistreatmentonadhesioncouldbeovercomebyfollowingwithanodiccleaning,usingatleastthesamequantityofampereminutespersquarefootandpreferablymore.
WehaveextendedthisapplicationofFaraday'sLawsbyincreasingtimeand/orcurrentdensityofboththeelectrolyticalkalineandacidtreatmentsindevelopingcleaning
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cyclesforspecificplatingapplications.Eachcyclesodevelopedmustbeshownbytesttomeettherequiredspecifications,especiallytheadhesion,beforebeingusedinproduction.Thenbycontrollingtheproductioncyclesteps,asestablishedbythisprocedure,thequalityoftheplatedproductcanbeassured.Afewillustrationsofhowthishasbeenappliedmaybeofinterest.
Platingchemicalequipment
ThelateCarlHeussnerused18cleaningstepsincludingrinsesforthefirstatomicenergyprogram(theManhattanProject)inthepreparationofsteelequipmentfornickelplating.Henaturallyincludedeveryfavorabletreatmentstepthathadbeenrecommendedintheliteratureinordernotonlytomeetthecorrosionandadhesionteststhatwerespecified,butinthehopethatthequalityofnickelplatingsoproducedwouldprovesatisfactoryfortheintendedservice.Fortunatelytheplatednickelcoatingsperformedsuccessfully.OtherwisesolidwroughtnickelwouldhavebeenrequiredandthisprogramalonewouldhaveconsumedtheavailableoutputofnickelinAmericafortwoyears.1Ofcourse,nosuchquantitywasavailable,soifplatinghadfailed,wemightnothavehadtheatombomb.
Theequipmentprogramsthatfollowedthewarwerenolongeronacrashbasisandmoneywasnolongerbeingspentonanemergencybasis.Itwasimportantthereforetolimitthenumberofpreplatingstepstoaminimuminordertoreduceplantinvestments.Fortunatelywehadthetimetoinvestigatethis.ByapplyingthequantitativeconceptofFaradayindevelopingthecleaningcyclewewereabletomeetthenickelplatingspecificationforboththeadhesionandhotwaterporosityratingwithacycleofonlyfoursteps,twoofwhichwererinses.2(SeeTable1.)
Weknewthatanodicalkalineandanodicsulfuricacidtreatmentsfavoredtheadhesionofnickeltomildsteel.Wedidnotknowwhatquantityofelectricityinthesetreatmentswasrequiredtomeetthespecificationsor,infact,whethersomefurthercyclevariationswouldberequired.Weincreasedthequantityofcurrentstepwiseinboththeanodicalkalineandacidtreatmentsandultimatelyfoundthatwithaminimumof300Amin/ft2inbothtreatmentswegotperfectadhesion.Thenonsilicatedproprietarycleanerthathadoriginallybeenspecifiedwasoperatedataconcentrationof1012oz/galandatemperatureof190200F.Theanodicacid50percentbyvolumesulfuricacidwasoperatedatatemperaturenotinexcessof85F.Aminimumcurrentdensityof50Amin/ft2andsixminutestreatmenttimewasusedinbothtreatments.
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Table1Cleaningcyclesfornickelplating.*
Itisconservativelyestimatedthatoverthreemillionsquarefeetofsurfacewereplatedtoanaverageof57milofnickelwithoutasinglefailureduetoadhesion.Whenapieceofsome700squarefeetofsurfacefailedtopassthehotwaterporositytestoccasionally,thedefectiveareaswerewirebrushed.Thepiecewasthengiventhesamecleaningtreatmentswithminormodificationpriortoplatingadditionalnickelovertheinitialcoating.Noadhesionfailurebetweenthetwonickelcoatingswaseverexperienced.
Inpractice,theanodicalkalineelectrolytictreatmentwassometimesincreasedtoasmuchas500Amin/ft2.Theanodicacidtreatmentwassometimesincreasedto1000Amin/ft2.Thiswasdonetocompensateforaparticularlybadlotofsteelorasafurtherfactorofsafety,especiallywhenplatingnickelovernickel.Inthelattercasewewerealwayscarefultousemoreampereminutespersquarefootintheacidtreatmentthanintheanodicalkalinetreatment,sincethelatteraloneadverselyaffectstheadhesionofnickelovernickel.
Onemustrealizethatthisapplicationofplatingwasforcorrosionresistanceinachemicalenvironmentandinvolvedtheuseofheavynickelcoatings.Abrightappearancewasofnoimportance.Thereforeetchingresultingfromthelonganodicacidtreatmentcouldbeusedtoadvantage.Theproblemisquitedifferentwhenplatingnickelovernickelforadecorativeapplication,asdiscussedinthenextexample,wherethecoatingsarethinnerandlusterissoimportant.
Platingnickelonbuffednickel
In1947theInternationalNickelCo.wantedtohavesomesteelpanelsplatedwithdoublenickelcoatingstobeincludedintheoutdoorexposureprogramofCommitteeB
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8ofASTM,nowknownasProgramNo.1.ThelotofpanelsrequiringafirstcoatingofbuffedWattstypenickel,followedbyasecondcoatingofthesamenickel,presentedaproblem.Onehadtocleanandactivatethefirstbuffednickelsurfacesothatthebuffedsurfacewouldnotbedestroyed,butatthesametimewouldinsureadequateadhesionofthesecondnickelcoating.Weknewcathodicalkalicleaningandastronghydrochloricaciddipwouldfavoractivationofthebuffednickelsurfaceandadhesionofthesecondnickelcoating.Wedidnotknowthequantityofcurrentrequiredtoaccomplishthis.InourlaboratoryevaluationofthecyclewekeptincreasingtheampereminutesofcathodiccleaninguntilasshowninCycle1ofTable2withtwoseparatetreatmentsof75Amin/ft2each,followedbyathreeminutedipin50volumepercenthydrochloricacid,weobtainedgoodadhesionofnickelonthebuffednickelsurface.Theadhesiononthebackofthetestpanelwherethesteelhadonlybeenroughpolishedandthefirstnickelcoatwasunbuffedwasstillverypoor.Bytheninsertingbetweenthetwocathodiccleaningstepsa15Amin/ft2anodicetchin30percentbyweightsulfuricacidasshowninCycle2,weobtainedexcellentadhesionofthesecondnickelcoatingonboththefrontandbackofatestpanel.BythusapplyingthequantitativeconceptofFaraday'sLawstocleaning,wedevelopedasatisfactorycycleanditisnowamatterofrecordthatthepanelssopreparedperformedwellwhentestedoutdoors.
Itisconservativelyestimatedthatoverthreemillionsquarefeetofsurfacewereplatedtoanaverageof57milofnickelwithoutasinglefailureduetoadhesion.Whenapieceofsome700squarefeetofsurfacefailedtopassthehotwaterporositytestoccasionally,thedefectiveareaswerewirebrushed.Thepiecewasthengiventhesamecleaningtreatmentswithminormodificationpriortoplatingadditionalnickelovertheinitialcoating.Noadhesionfailurebetweenthetwonickelcoatingswaseverexperienced.
Inpractice,theanodicalkalineelectrolytictreatmentwassometimesincreasedtoasmuchas500Amin/ft2.Theanodicacidtreatmentwassometimesincreasedto1000Amin/ft2.Thiswasdonetocompensateforaparticularlybadlotofsteelorasafurtherfactorofsafety,especiallywhenplatingnickelovernickel.Inthelattercasewewerealwayscarefultousemoreampereminutespersquarefootintheacidtreatmentthanintheanodicalkalinetreatment,sincethelatteraloneadverselyaffectstheadhesionof
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nickelovernickel.
Onemustrealizethatthisapplicationofplatingwasforcorrosionresistanceinachemicalenvironmentandinvolvedtheuseofheavynickelcoatings.Abrightappearancewasofnoimportance.Thereforeetchingresultingfromthelonganodicacidtreatmentcouldbeusedtoadvantage.Theproblemisquitedifferentwhenplatingnickelovernickelforadecorativeapplication,asdiscussedinthenextexample,wherethecoatingsarethinnerandlusterissoimportant.
Platingnickelonbuffednickel
In1947theInternationalNickelCo.wantedtohavesomesteelpanelsplatedwithdoublenickelcoatingstobeincludedintheoutdoorexposureprogramofCommitteeB8ofASTM,nowknownasProgramNo.1.ThelotofpanelsrequiringafirstcoatingofbuffedWattstypenickel,followedbyasecondcoatingofthesamenickel,presentedaproblem.Onehadtocleanandactivatethefirstbuffednickelsurfacesothatthebuffedsurfacewouldnotbedestroyed,butatthesametimewouldinsureadequateadhesionofthesecondnickelcoating.Weknewcathodicalkalicleaningandastronghydrochloricaciddipwouldfavoractivationofthebuffednickelsurfaceandadhesionofthesecondnickelcoating.Wedidnotknowthequantityofcurrentrequiredtoaccomplishthis.InourlaboratoryevaluationofthecyclewekeptincreasingtheampereminutesofcathodiccleaninguntilasshowninCycle1ofTable2withtwoseparatetreatmentsof75Amin/ft2each,followedbyathreeminutedipin50volumepercenthydrochloricacid,weobtainedgoodadhesionofnickelonthebuffednickelsurface.Theadhesiononthebackofthetestpanelwherethesteelhadonlybeenroughpolishedandthefirstnickelcoatwasunbuffedwasstillverypoor.Bytheninsertingbetweenthetwocathodiccleaningstepsa15Amin/ft2anodicetchin30percentbyweightsulfuricacidasshowninCycle2,weobtainedexcellentadhesionofthesecondnickelcoatingonboththefrontandbackofatestpanel.BythusapplyingthequantitativeconceptofFaraday'sLawstocleaning,wedevelopedasatisfactorycycleanditisnowamatterofrecordthatthepanelssopreparedperformedwellwhentestedoutdoors.
Table2Cleaningcyclesfornickelplatingoverbuffednickel.*
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Nickelplatingovernickelreruns
Defectivenickelchromiumplatedsteelparts,suchasbumpers,arefrequentlysalvagedbyfirststrippingthechromium,thenpolishingoutthedefectsandrenickelplating.Variouscyclesareuseddependingtoalargedegreeuponthetreatmentsavailableinagivenplatinginstallation.ThefollowingillustrateshowFaraday'sLawswereappliedinonecaseforevaluatingacleaningcycleforthispurpose.
Table3Cleaningcyclesfornickelplatingoverpolishednickel.*
TwocleaningcyclesAandBinTable3werefirstevaluated.Omittinganyreferencetorinsinginbetweentreatments,bothcyclesincludedaoneminutealkalisoakand30A
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min/ft2ofcathodicelectrocleaningwitha15second2Nhydrochloricaciddippriortonickelplating.TheonlydifferencebetweenthetwocycleswasthatBhadinadditiona35Amin/ft2anodicelectrocleaningstepinsertedaheadoftheaciddip.CycleAthereforehadbut30Amin/ft2cathodiccleaningwhileCycleBhadatotalof65Amin/ft2ofelectrocleaning,thelast54percentofwhichwasanodic.InspiteofthisadditionalelectrocleaningadhesionbetweenthefirstandsecondnickelcoatingswhenusingCycleBwasratedpoorwhileAwasratedgood.
AthirdCycleCwasthenevaluatedinwhichthefirsttwotreatmentstepswerecathodicelectrocleaningforacombinedtotalof70Amin/ft2.Thiswasfollowedbythesame15second2Nhydrochloricaciddippriortonickelplating.CycleCgaveexcellentadhesionbetweenthetwonickelcoatingscomparedtoCycleAwhichonlyratedgood.Thisdifferencewasobtainedbysubstitutingacathodicelectrocleanerforthealkalisoakinstep1ofCycleA,andtherebyincreasingthequantityofcathodiccleaningfrom30to70Amin/ft2.
Platingbimetalsurfaces
Whenplatingrerunsofnickelplatedsteelpartsacomplicationarisesif,inremovingthenickelcoatingdefectsbypolishing,steelareasareexposed,becauseoptimumadhesiononsteelisfavoredbyanodictreatmentswhilecathodictreatmentsarebestfornickel.Agoodcompromiseinvolvestheuseofananodicelectrocleaningtreatmentfollowedbyananodicacidtreatment,acathodicelectrocleaningtreatmentandahydrochloricaciddipasshowninColumn2ofTable4.Thelastthreetreatmentsallactivatethenickel,thusfavoringadhesionwhenplated.Thecathodicelectrocleaningwhichisunfavorabletosteelshouldpreferablybewithalessquantityofcurrentthantheanodicelectrocleaning.Theanodicacidtreatmentwhichisbeneficialtoadhesiononbothnickelandsteelshouldalwaysemployagreaterquantityofcurrent,thaneitherofthealkalineelectrocleaningtreatments.Therequiredampereminutespersquarefootforeachelectrolytictreatmentshouldbedeterminedbytesttoobtainoptimumadhesion.
Therearemanyothercasesofplatingovertwodifferentmetalsononeobjectinwhichdifficultyisexperienced.OnecasewhereFaraday'sLawswereappliedinvolvedtheplatingofbrasspartswithsolderedjoints.ThecleaningcyclethatprovedmostsuccessfulasshowninColumn3ofTable4consistedoffoursteps,namely,asoakcleaner,90Amin/ft2inacathodicelectrocleaner,195Amin/ft2ina20Bcathodic
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sulfuricacidtreatment,and120Amin/ft2inacopperstrike.Itisnecessarytousesufficientampereminutespersquarefootintheelectrolytictreatmentstoreducetheoxidesformedinsolderinginordertogetadherentplatedcoatings.Theappearanceofthesurfaceaftertheacidtreatmentmaybefarfrompleasing,butthisinnowayimpairstheappearanceorqualityofplatedcoatingswhichmaybeapplied.
PlatingStelliteandHastalloyC
InoneengineeringapplicationrequiringadherentnickelplatingonStellite,Faraday'sLawswereagainappliedtoadvantageinthedevelopmentofthepreparatorycleaningcycleasshowninColumn4ofTable4.Thedesiredresultswerefinallyobtainedwithacycleinvolvingtreatmentsof200Amin/ft2ofanodicelectrocleaning,50Amin/ft2ofanodic50volumepercentsulfuricacid,a5seconddipin10volumepercenthydrochloricacidandaWood'snickelchloridestrikeof300Amin/ft2priortoplating.
ThissamecyclealsowasusedsuccessfullyforadherentlyplatingsomeHastalloyCandCarballoyparts.
Table4Cleaningcyclesforplating
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Platingtheexoticmetals
Aqualifyingwordisinorderwithrespecttocleaningtheexoticmetalspriortoplating.Theirchemistryissodifferentfromthemorecommonbasismetalsthatothertreatments,specificallyforagivenmetal,mayhavetobeadded.Thisistheareainwhichmuchremainstobelearned.However,totheextentthatelectrolytictreatmentsareinvolved,theapplicationofFaraday'sLawshasprovenfruitful.
Inconclusion,maywesummarizeasfollows:
Assumingtheremovalofthevaryingamountsofmanydifferentorganicsoilsinpreliminarycleaningsteps,thesubsequentelectrolyticcleaningandactivatingtreatmentsdetermineboththeadhesionandqualityoftheplatedcoating.
Therearethreeelectrolytictreatments,buildingblockssotospeak,commonlyusedindevelopingasuccessfulcycle:
1. Electrolyticalkalicleaning.2. Anacidtreatment,frequentlyelectrolytic.3. Astrike(usuallyWood'snickelchloridestrike),acathodictreatment,if
allowableandnecessary.Wewoulddiscouragethepracticeofsimplycopyingspecifictreatmentsoracombinationofstepsasreportedintheliteraturewhensearchingforacycletoperformadifficultjobofcleaningbeforeplating.Oneverygoodreasonisthefactthatjustchangingaproprietarycleanermaychangetheresults.Butthen,therearemanyotherreasons.
Onthebasisofoursuccess,werecommendinsteadtheapplicationofFaraday'sLawstoalltheelectrolytictreatmentstepsinthedevelopmentofanycycleandtothedegreenecessarytoattainthedesiredadhesionandquality.
OnlytotheextenttowhichthisispracticedcanonelearntoappreciatethefullsignificanceofFaraday'sLawsasappliedtocleaningbeforeplating.
References
1.W.W.Stout,"Secret,"ChryslerCorporation,Detroit(1947).
2.F.K.Savage,A.K.GrahamandE.P.Strothman,MaterialsandMethods,August1952.
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3.A.K.Graham,Trans.Inst.Met.Finishing,31,259266(1954).
AboutDr.A.KennethGraham(fromthebiographyprintedin1959atthetimeofhisreceivingtheAESScientificAchievementAward)
Dr.A.KennethGrahamwasborninPhiladelphia,December25,1896.Heattendedthepublicschools.UpongraduatingfromtheCentralHighSchoolin1915,hewasawardedaCityscholarshiptotheUniversityofPennsylvania.HegraduatedwithaB.S.degreeinChemicalEngineeringinJune1919,afterhavingservedtenmonthsin1918withtheU.S.MarinesinWorldWarI.
HethenworkedintheresearchdepartmentoftheScovillMfg.Co.,Waterbury,Conn,fortwoyears.DuringthistimehemetandworkedwithGeorgeB.Hogaboom.Thiswasthebeginningofalifelongfriendship.ItwasthroughthisassociationthatDr.Grahambecameinterestedinelectroplatinganddecidedtospecializeinthisfield.
SincetherewasnomoderntextonplatinguntilBlumandHogaboompublishedtheirbookin1923,Dr.Grahamdecidedthebestwaytolearnaboutplatingwastoworkatit.Thishedidasaplater'shelperfromOctober1920untilJuly1921firstattheHartfordSterlingCo.,Philadelphia,andthenattheWelsbachCo.,Gloucester,N.J.
Thesummerof1921,Dr.GrahamstudiedmetallographyatColumbiaUniversity.ThiswasfollowedbyfiveyearsinthegraduateschooloftheUniversityofPennsylvania,duringwhichtimeheservedasInstructorinChemistryandcompletedworkleadingtoatechnicaldegreeofCh.E.andgraduatedegreesofM.S.andPh.D.
Afterasixmonthboutwithanulcer,Dr.GrahamdeliveredhisfirstpaperbeforetheAESattheconventioninNewarkinJune1926,forwhichhelaterreceivedamedalaward.
HethenjoinedtheHansonVanWinkleCompanyofNewark,N.J.andbecameassociatedwithGeorgeHogaboomforthesecondtime.HeinstalledalaboratoryatNewarkandlateratMatawan,N.J.,whentheHansonCompanyjoinedwithMunning.Duringthisperiodthesimplifiedmethodsofanalysisforplatingbathsweredeveloped,thecourseforplaterswasfirstoffered,thestandardsolutionsforanalysesweremadeavailableforplaters,andthezincaluminumanode,whichlaterbecamepatented,wasdeveloped.
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Startinginthefallof1928,Dr.Grahamheldthefollowingpositions:
UniversityofPennsylvania,Philadelphia,Pa.,InstructorandAssistantProfessorinChemicalEngineering,September1928toFebruary1937.KennethGraham&Associates,Jenkintown,Pa.,ConsultingEngineer,July1936toJune1942.WarProductionBoard,Washington,D.C.,PlatingConsultantandDeputyChief,ProductsBranch,ConservationDivision,June1942toJune1943.HoudailleHersheyCorp.,Decatur,Ill.,DirectorofResearchandDevelopment,GarfieldDivision,June1943toAugust1944.Graham,Crowley&Associates,Inc.,(laterbecomingGraham,Savage&Associates,Inc.),Jenkintown,Pa.,President,September1944todate[asofthiswritinginJune1959Ed.].
Dr.GrahamjoinedtheNewarkBranchoftheAESin1926.In1928,hetransferredtothePhiladelphiaBranch.HeorganizedandtaughtthefirstchemistryclassforthePhiladelphiaBranchoftheAES.HehaswonthreegoldmedalawardsforpapersfromtheAES.HeservedasExecutiveSecretaryoftheSocietyfrom1945to1951,duringwhichtimethemonthlypublicationwaschangedfromthesmallsizeMonthlyReviewtothepresentformatofPlating.HewaselectedanHonoraryMemberofthePhiladelphiaBranchin1957.
HeisalsoamemberoftheInstituteofMetalFinishing,ASTM,ACS,AIChE,AssociationofConsultingChemistsandChemicalEngineers,Inc.,andTheElectrochemicalSociety.HehasbeenactiveoncommitteesofmostofthesesocietiesandservedasmanagerandvicepresidentofTheElectrochemicalSocietyforelevenyears.
Hehaspublishedoverfortytechnicalpapers,obtainedseveralpatents,contributedchapterstoModernElectroplatingbyGray,theACSMonographonCopperbyButts,andtheElectroplatingEngineeringHandbook,forwhichhealsoservedasEditorinChief.
CommentsarereviewedbymoderatorsbeforetheyappeartoensuretheymeetProductsFinishingssubmissionguidelines.
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4/23/2015 FaradaysLawAppliedtoCleaning:ProductsFinishing
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