The Electrodeposition of Zinc-Bismuth Alloys

Biphasic nanocrystalline zinc-bismuth alloys containing between 15 and 90 wt% of bismuth have been electrodeposited on copper sheets and brass cylinders from acidic electrolytes. Complexation of Bi 3+ by gluconate in the zinc sulfate/ bismuth methanesulfonate containing electrolyte was not sufficient to shift the reduction potential of Bi 3+ close enough to that of Zn 2+ . Burnt deposits could be avoided only by using additives that kinetically hinder the reduction of Bi 3+ . The additive effects on Zn-Bi plating have been studied by cyclic voltammetry and electrodeposition in the Hull and Rota-Hull cell. Thickness and composition of the layers were determined by X-ray fluorescence and energy dispersive analysis of X-rays. The microstructure and crystallite size of the alloys have been studied by scanning electron microscopy and X-ray diffraction.