Yutaka Tsuru

Application of vapor-deposited carbon and zinc as a substitute for palladium catalyst in the electroless plating of nickel

A new electroless nickel plating technique is described which eliminates the conventional use of palladium catalyst. Using a physical vapor deposition technique, layers of carbon and of zinc of approximately 10 and 20 nm thickness, respectively, were deposited onto an ABS resin substrate on which had previously been adsorbed a colloidal mixed hydroxide containing nickel ions and copper ions. The electrons released by the oxidative dissolution of the zinc layer into the plating solution were utilized to reduce the colloids to metallic nickel and copper, which served as an anchor for the subsequently plated nickel films. The peeling strengths of the electroless nickel films resulting from the application of this technique were in the order of 200 kg/m, in contrast to values of approximately 220 kg/m obtained using a conventional tin (2+) sensitizer and palladium (2+) activator.

Evaluation of the Amount of Hydrogen Gas and Induction Period Occurred during Pitting Corrosion of Iron

An electronic balance was used to investigate the time-variation of the amount of hydrogen gas evolved during anodic dissolution of iron corresponding to electric charges of 5.0 C at 20 mA/cm current density. The electrodes were made of commercial type iron of 99.5% purity. The corrosive solutions were a chloride-sulfate mixed bath of pH 8.0(0.5 M NH4Cl 0.5 M Na2SO4 0.1 M H3BO3 0.1 M Na2B4O7). Use of an electronic balance enabled in situ measurements of the buoyancy attributable to the hydrogen gas bubble formed during the pitting corrosion of the iron. Measurements also elucidated the induction period from the beginning of electrolysis until hydrogen gas formation. The results indicate that a strongly corrosive solution formed progressively in the pits brought about chemical dissolution of iron followed by hydrogen gas evolution.

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.

Study on brass electrodeposition by pulse electrolysis from cyanide plating bath.

Pulse plating of Cu-Zn alloy from cyanide brass plating baths was investigated with respect to the effect of pulse electrolysis with galvanostatic square pulses on the potential-current curves, current efficiency and composition of brass deposit. It was found that pulse plating yielded a brass deposit of uniform composition with a brighter appearance and finer crystal grain than that obtained under direct current electrolysis, and that the effect of pulse plating at a high pulsed-current density was mainly influenced by the increased deposition overpotential and the off period in each cycle where there is zero current in the external circuit. It was also noted that the electrodeposition mechanism changed from the regular type to the irregular type with increasing pH in the vicinity of electrode surface, since high pulsed current electrolysis resulted in a greatly increased hydrogen evolution reaction.