Abstract
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.
