To clarify the effect of chloride ions on the deposition behavior and crystal morphology of Zn at initial stage from electrowinning solutions, the partial polarization curve, current efficiency and AC impedance for Zn deposition and the morphology and crystal orientation of deposited Zn were investigated. In solutions containing chloride ions, the partial polarization curve for Zn deposition was evidently depolarized and the polarization resistance was decreased. With increasing the concentration of chloride ions from 600 to 6000 mg/L, the degree of depolarization and decrease in polarization resistance became significantly large. On the other hand, the partial polarization curve for hydrogen evolution was almost unchanged by the presence of chloride ions. As a result, the current efficiency for Zn deposition of initial stage at current densities from 100 to 2000 A/m2 increased by 3 to 10 % with chloride ions. The crystal of Zn deposited from the solutions containing chloride ions became aggregated and large. This tendency was remarkable with increasing the concentration of chloride ions to 6000 mg/L. In Zn deposition at 500 A/m2, the orientation index of {0001} plane and the crystallite size of Zn increased a bit with chloride ions. This is attributed to the decrease in overpotential for Zn deposition with chloride ions.
