Complexing agents for a Zn–Ni alkaline bath

Zinc–nickel alloys were obtained from alkaline electrolytes. Four amines, all of which are good complexing agents for nickel, were tested to identify their effects on the deposition process and final plate. The influence of THEED, an additive commonly used with alkaline electrolytes, was also examined. The electrochemical analysis showed some differences between acid and alkaline deposition processes, but no great influence was observed for the amine type. All four amines gave a consistent nickel content throughout the range of currents tested. The main difference was obtained in the structure of the alloys since some of the coatings showed an η-phase with an unusually high Ni content.