Voltammetric and morphological characterization of zinc electrodeposition from acid electrolytes con

Voltammetric and morphological characterization of zinc electrodeposition from acid electrolytes con

JApplElectrochem(2008)38:1203–1210DOI10.1007/s10800-008-9534-2

ORIGINALPAPER

Voltammetricandmorphologicalcharacterizationofzincelectrodepositionfromacidelectrolytescontainingboric–polyalcoholcomplexes

E.M.deOliveiraÆI.A.Carlos

Received:24October2007/Revised:26February2008/Accepted:26February2008/Publishedonline:13March2008ÓSpringerScience+BusinessMediaB.V.2008

AbstractThein uenceofsorbitolorglycerolpolyalco-holsontheelectrodepositionofzincandonmorphologyofthezinc lmisdiscussed.Thedepositioncurrentef -ciency,inthepotentialrange-1.30Vto-2.50V,was*90%inallbaths.Increasingthesorbitolconcentrationinthebathshiftedthedepositiontomorenegativepotentials,*50mV,anddecreasedthecurrentdensity(jp)ofthezincdepositionsigni cantly.Ontheotherhand,addingglyceroldidnotsigni cantlyaffecteitherjorthedepositionpotentialofzinc.Scanningelectronmicroscopy(SEM)showedthateithersorbitolorglycerolleadtotheformationofgranulardeposits.Thebestzincmorphologywasobtainedwith0.52Msorbitolorglycerolintheplatingbath.Thepresenceofsorbitolorglycerolintheplatingbathwasbene cial,sincetheresultingzincdepositswerecompactandwithoutholes.

KeywordsElectrodepositionÁZincÁSorbitol–boriccomplexÁGlycerol–boriccomplex

1Introduction

Zincelectrocoatingshaveforalongtimebeenwidelyusedtoprotectsteelfromcorrosionandthereisaconsiderablerecordofdataonzincelectrodepositionindifferentelec-trolyticsolutions[1].Organicandinorganiccompoundsintheelectrolyteplayanimportantroleinmetalplating,astheyfacilitatetheformationofuniformoverlayersofhighbrightness.Suchadditivesdonottakepartinthedeposition

E.M.deOliveiraÁI.A.Carlos(&)

´mica,UniversidadeFederaldeSa oCarlos,DepartamentodeQu

CP676,SaoCarlos,SP13565-905,Brazile-mail:diac@ufscar.br

reactiondirectlybuttheyin uencethenucleationandgrowthofthedepositandconsequentlythe lmmorphol-ogy[2].

Leeetal.[3]studiedtheeffectsoforganicadditivessuchasbenzoicacid(BA)andpolyethyleneglycol(PEG)ontheinitialstagesofzincelectroplating.BAmainlycontributedtothecontrolofroughnessofthezinclayer,interactingweaklywithzincions.However,PEGmole-culesraisetheoverpotentialsforreductionofbothzincionsandprotonsbyeffectivelyblockingtheelectrodesurface.MackinnonandBrannen[4]studiedtheeffectsofaddingvariousorganiccompoundstoaZnCl2electrolyteonzincdepositmorphologyandcrystalliteorientation.Tetrabutylammoniumchloride(TBACl)wasthemosteffectiveofseveraltetraalkylammoniumchloridesinsmoothingandre ningthegrainandeliminatingdendriticgrowth.RobinsonandO’Keefe[5]studiedtheeffectsofantimonyandglueonzincelectrowinningandconcludedthatantimonyre nedthegrainsizeandglueleveledthedepositsbypreventingdendriticgrowth.Mackinnonetal.[6]studiedtheeffectofthiourea,withandwithouttheadditionofglueandantimony,onthezincdepositioncurrentef ciency(CE),aswellasonthemorphologyandorientationofzincdeposits.IncreasingconcentrationsofthioureadecreasedtheCEandtheadditionalpresenceofantimonydidnotsigni cantlyalterthiseffect,whichtheadditionofglueresultedinafurthersubstantialdecreaseinCE.Thioureachangedthezincdepositmorphologyandorientation,andalteredtheshapeofthezincdepositioncyclicvoltammogram.Zincelectrodepositionathighcur-rentdensitywasstudiedbyKaravastevaandKaraivanov[7]andThomasandFray[8].The rstauthorsinvestigatedtheeffectofsomesurfactantsonthestructureofthedeposit,currentdensity,cellvoltage,speci cenergycon-sumptionandthepurityofzincmetalelectroextractedat

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