Properties of Tin-Zinc Alloy Deposits from Gluconate Baths

In the preceding paper, there were reported the plating methods of tin-zinc alloys from the baths free from cyanides and fluorides. It was found that low zinc content alloy deposits having good appearance were obtained from gluconate baths. In this paper, there are discussed some properties of tin-zinc alloy deposits obtained from gluonate baths; namely, effects of o-vanillin as a brightener, corrosion resistance, hardness, and whisker growth. The following results were obtained (1) The surface of a tin-zinc alloy deposit containing almost equimolar ratio between zinc and tin was smoother than that of single tin or zinc deposit: and the structure of the former was much finer than that of the latter. (2) The brightening effect of o-vanillin on the alloy plating seemed to be due to the crystal growth of tin, not of zinc. (3) The tin-zinc alloy deposits had high corrosion resistance and their sacrificial protective actions were retained in the range of 2-3% of zinc contents of the deposits. (4) The tin-zinc alloy deposits had high solderability and their hardness vas slightly higher than that of cast alloys. No whisker growths were found on their surfaces.