NUCLEATION AND GROWTH OF ZINC ELECTRODEPOSITS ON A POLYCRYSTALLINE ZINC ELECTRODE IN THE PRESENCE OF CHLORIDE-IONS

The kinetics of the nucleation and growth of zinc on a zinc electrode in 0.1 m ZnCl2 has been studied by the potential step technique. Four supporting electrolytes were used: 0.5 m NaCl, 1 M NaCl, 3 M NaCl and 1 m NaClO4. The current decays to a minimum, after which it rises to a maximum and then decreases again. The initial part of the transient, up to the current minimum, includes the double layer charging and the initial nucleation and growth of zinc. The rising part of the transition curve, from the current minimum to the maximum, follows the model of progressive nucleation and diffusion-controlled, hemispherical three dimensional growth. The steady state nucleation rate and the nuclear number density increase with the overpotential and with the NaCl concentration. The results point to a direct involvement of zinc chlorocomplexes in the electrodeposition process.