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

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