Abstract:
Cementation of copper onto zinc from a sulfate bath was investigated through polarization measurements of both the anodic and cathodic half-cell reactions as well as practical cementation studies. Individual half-cell reactions, when isolated in a dual cell, followed a first-order rate with respect to [Cu2+] (cathodic) without any excess zinc dissolution (at the anode) via a hydrogen reaction. In the presence of a zinc surface and Cu2+ in single bath, excess zinc dissolved via hydrogen reduction and the first-order copper cementation rate was enhanced after an initial slow step. The enhanced rate is associated with a decrease of the mixed potential, E-m. Deposited copper catalyzes, excess zinc dissolution via hydrogen reduction reaction. (C) 2000 The Electrochemical Society. S0013-4651(99)04-103-8. All rights reserved.