faraday’s law applied to cleaning _ products finishing

4/23/2015 FaradaysLawAppliedtoCleaning:ProductsFinishing

http://www.pfonline.com/articles/faradayslawappliedtocleaning 1/17

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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



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



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



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



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.



Table1Cleaningcyclesfornickelplating.*

Itisconservativelyestimatedthatoverthreemillionsquarefeetofsurfacewereplatedtoanaverageof57milofnickelwithoutasinglefailureduetoadhesion.Whenapieceofsome700squarefeetofsurfacefailedtopassthehotwaterporositytestoccasionally,thedefectiveareaswerewirebrushed.Thepiecewasthengiventhesamecleaningtreatmentswithminormodificationpriortoplatingadditionalnickelovertheinitialcoating.Noadhesionfailurebetweenthetwonickelcoatingswaseverexperienced.

Inpractice,theanodicalkalineelectrolytictreatmentwassometimesincreasedtoasmuchas500Amin/ft2.Theanodicacidtreatmentwassometimesincreasedto1000Amin/ft2.Thiswasdonetocompensateforaparticularlybadlotofsteelorasafurtherfactorofsafety,especiallywhenplatingnickelovernickel.Inthelattercasewewerealwayscarefultousemoreampereminutespersquarefootintheacidtreatmentthanintheanodicalkalinetreatment,sincethelatteraloneadverselyaffectstheadhesionofnickelovernickel.

Onemustrealizethatthisapplicationofplatingwasforcorrosionresistanceinachemicalenvironmentandinvolvedtheuseofheavynickelcoatings.Abrightappearancewasofnoimportance.Thereforeetchingresultingfromthelonganodicacidtreatmentcouldbeusedtoadvantage.Theproblemisquitedifferentwhenplatingnickelovernickelforadecorativeapplication,asdiscussedinthenextexample,wherethecoatingsarethinnerandlusterissoimportant.

Platingnickelonbuffednickel

In1947theInternationalNickelCo.wantedtohavesomesteelpanelsplatedwithdoublenickelcoatingstobeincludedintheoutdoorexposureprogramofCommitteeB



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



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.*



Nickelplatingovernickelreruns

Defectivenickelchromiumplatedsteelparts,suchasbumpers,arefrequentlysalvagedbyfirststrippingthechromium,thenpolishingoutthedefectsandrenickelplating.Variouscyclesareuseddependingtoalargedegreeuponthetreatmentsavailableinagivenplatinginstallation.ThefollowingillustrateshowFaraday'sLawswereappliedinonecaseforevaluatingacleaningcycleforthispurpose.

Table3Cleaningcyclesfornickelplatingoverpolishednickel.*

TwocleaningcyclesAandBinTable3werefirstevaluated.Omittinganyreferencetorinsinginbetweentreatments,bothcyclesincludedaoneminutealkalisoakand30A



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



sulfuricacidtreatment,and120Amin/ft2inacopperstrike.Itisnecessarytousesufficientampereminutespersquarefootintheelectrolytictreatmentstoreducetheoxidesformedinsolderinginordertogetadherentplatedcoatings.Theappearanceofthesurfaceaftertheacidtreatmentmaybefarfrompleasing,butthisinnowayimpairstheappearanceorqualityofplatedcoatingswhichmaybeapplied.

PlatingStelliteandHastalloyC

InoneengineeringapplicationrequiringadherentnickelplatingonStellite,Faraday'sLawswereagainappliedtoadvantageinthedevelopmentofthepreparatorycleaningcycleasshowninColumn4ofTable4.Thedesiredresultswerefinallyobtainedwithacycleinvolvingtreatmentsof200Amin/ft2ofanodicelectrocleaning,50Amin/ft2ofanodic50volumepercentsulfuricacid,a5seconddipin10volumepercenthydrochloricacidandaWood'snickelchloridestrikeof300Amin/ft2priortoplating.

ThissamecyclealsowasusedsuccessfullyforadherentlyplatingsomeHastalloyCandCarballoyparts.

Table4Cleaningcyclesforplating



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.



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.



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.

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faraday’s law applied to cleaning _ products finishing

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