Dependence of coating characteristics on deposition potential for electrodeposited Zn-Ni alloys

The electrodeposition of zinc-nickel alloys from ammonium chloride baths wa s studied on different substrates under potentiostatic and galvanostatic co nditions, from low potentials/current densities where the codeposition was normal to the conditions where anomalous deposition took place. Anodic line ar sweep voltammetry (ALSV) and ex situ techniques were used to characteriz e the coatings obtained in each condition. The results indicated that three deposition potential zones could be defined corresponding to practically p ure nickel, alpha- and gamma-phase domains. It was observed that the abrupt change in alloy composition and current efficiency that occurred during po tentiostatic deposition did not correspond to the transition from normal to anomalous codeposition. In our conditions, this change always coincided wi th the appearance of gamma-phase in the coatings. (C) 1999 Elsevier Science Ltd. All rights reserved.