ELECTRODEPOSITION OF ZINC NICKEL-ALLOY COATINGS FROM A CHLORIDE BATH CONTAINING NH4CL

Zinc-nickel alloys were electrodeposited on steel from chloride baths containing NH4Cl using different plating conditions. Current density, temperature and nickel percentage in the baths were found to strongly influence the composition of the deposits and the morphology. At low current densities transition from anomalous to normal codeposition was observed. The changes in potential, current efficiency, composition and morphology which follow the transition were studied. No increase in the partial current of hydrogen reduction was observed at the potential values from which anomalous codeposition begins; this fact, plus the formation of zinc ammonium complexes, seems to exclude the precipitation of zinc hydroxide at the electrode surface. The electrodeposition of zinc-nickel alloys is discussed emphasizing the importance of kinetic parameters and cathodic potentials.