Toshihisa Hara

Study on Electroplating of Palladium-Nickel Alloy from Ethylenediamine Bath. I. Study by Potentiostatic Electroplating.

At pH 7, the occlusion of hydrogen in the alloy deposits decreased markedly compared to that in single deposits of palladium. Smooth, bright deposits could be obtained over a potential range of -0.7 to -1.1V vs Ag/AgCl. The palladium content of the alloy deposits increased with [en]/[M] ratio, whereas current efficiency decreased with increases in the potential and the ratio.When the [en]/[M] ratio exceeded 3 at pH 9, current efficiency decreased markedly due to the decrease in the deposition rate of nickel and the acceleration of hydrogen deposition. Palladium content showed its maximum value of 94% at a ratio of 3, and decreased at higher ratios. Smooth deposits could be obtained even at potentials as low as -1.1V from baths having a high [en]/[M] ratio at a pH above 8. This suggests that ethylenediamine acts not only as a complexing agent but also as a leveling agent.