Characteristics of Ni deposition in an alkaline bath for Zn–Ni alloy deposition on steel plates

Abstract

The characteristics of Ni deposition in an alkaline bath have been studied to provide the appropriate deposition conditions for Zn–Ni alloy deposition on steel plates using rotating disc electrode equipment. Triethanolamine (TEA) was used as an additive for maintaining the metal species in solution, and the effect of its use on the codeposition was also examined. The Ni content in the deposition layer was depressed at high current density where Zn deposition was predominant. It was also necessary to keep the concentration of Ni less than 0.8 g/dm 3 in the bath at a current density of 3 A/dm 2 so as to keep the Ni content less than 10 wt.% in the alloy layer. The Ni content was not influenced significantly by the concentration of TEA in the bath. As the rotation speed of the disc was increased, an anomalous codeposition has been observed, in that the deposition of Zn was predominant over that of Ni. It was also found that the Ni content was nearly constant below 50°C, while it increased sharply with increasing temperature above 60°C.