Kazumi Nishimura

Effects of Pulse Plating on Zn-Ni Alloy Electrodeposition Behavior

The effects of pulse parameters on the surface morphology, structure and electrodeposition behavior of Zn-Ni alloys were investigated by galvanostatic pulse plating The Ni content of Zn-Ni electrodeposits changed with average puls current density (Ia). This behavior was similar to that found in DC electrodeposition At current density of 1A/dm2 or less, Ni deposition and H2 evolution occured, while above 1A/dm2, Zn was deposited and abnormal Zn-Ni co-deposition began. Above 10A/dm2, Ni content increased with increases in Ia Pulse-plated Zn-Ni crystals were smaller than those obtained by DC electrodeposition Pulse period (T) also had a major effect on crystal size Off time (toff) affected the Ni content and the structure of the Zn-Ni electrodeposits With Ni content and γ phase increasing, while η phase decreased with increases in toffPolarization curves showing variations in pulse duty (ton/T) reflected Zn-Ni electrodeposition behavior The limited current density of abnormal electrodeposition (about 08A/dm2) gradually decreased with lower pulse duty Diffusion-controlled current densities above 10A/dm2 increased in accordance with pulse duty Initial deposits during pulse plating contained a Zn-enriched Zn-Ni layer, results which correspond to the theory of abnormal co-deposition