Alloy formation at electrodeposited zinc-copper electrode interfaces at room temperature

Electrochemical Zn deposition and stripping on Cu rod and foil electrodes in 35% KOH-containing zincates were examined to study Zn/Cu interfacial processes. In the cathodic potential scan, two apparent underpotential depositions at -1.1 and -1.3 V vs Hg/HgO and Zn-Cu alloy phase formation were observed. The alloy phase growth was clearly identified by a combination of electrochemical and X-ray diffraction measurements. The alloying rate at the Zn/Cu interface was evaluated by measuring the changes in the time interval of the potential plateau in the chronopotentiometry upon aging at room temperature. A simple semi-infinitive diffusion model based on the Zn density gradient within the Cu solid region in the vicinity of the interface allowed calculation of the Zn diffusivity in the Cu bulk, which was as high as 4.4x10(-15) cm(2)/s. Such a high diffusivity of Zn atoms in Cu was attributed to the lattice vacancies commonly present in Cu specimens. (C) 2008 The Electrochemical Society.