New insight into the anomalous codeposition of alloys

A new model for the anomalous codeposition of alloys is based on the kineti c characteristics of metal electrodeposition and th effect of hydrogen evol ution accompanying the deposition. The less noble metal has intrinsically f aster kinetics and so tis deposition rate can be controlled manly by diffus ion mass transfer in a certain range of over potentials; the convection ind uced by hydrogen evolution can speed up the relative deposition rate of thi s less noble metal when it is mainly diffusion-influenced. In contrast with previous models, such as the hydroxide suppression hypothesis, the monohyd roxide-discharge-controlled mechanism, and the competitive adsorption effec t, our model can explain naturally and completely anomalous codeposition, i .e. the preferential deposition of the less-noble metal, oa problem in allo y electrodeposition that has persisted for a century.