NUCLEATION AND GROWTH OF ZINC FROM CHLORIDE CONCENTRATED-SOLUTIONS

The electrodeposition of metals is a complex phenomenon influenced by a number of factors that modify the rates of nucleation and growth and determine the properties of the deposits. In this work we study the i nfluence of the zinc chloride (ZnCl2) concentration on the zinc nuclea tion process on glassy carbon, in a KCl electrolyte under conditions c lose to those employed in commercial acid deposition baths for zinc. T he electrochemical study was performed using cyclic voltammetry and po tentiostatic current-time transients. The charge-transfer coefficient and the formal potential for ZnCl2 reduction were evaluated from cycli c voltammetry experiments. The nucleation process was analyzed by comp aring the transients obtained with the known dimensionless (i/i(m))(2) vs. t/t(m) reponse for instantaneous or progressive nucleation. The r esults show that the nucleation process and the number density of site s are dependent on ZnCl2 concentration. Scanning electron microscopy a nalysis of the deposits shows that the deposits are homogeneous and co mpact although a change in the morphology is observed as a function of ZnCl2 concentration. Evaluation of the corrosion resistance reveals t he influence of the nucleation process on the subsequent corrosion res istance of the zinc deposits.