Abstract
Scanning electron microscopic studies were carried out in connection with the surface appearance of the Ag-Zn alloys electrodeposited from cyanide bath with various kinds of current forms. In the direct current plating, the needle-like deposits were obtained at lower current densities, which changed to granular in shape at higher current densities. In the pulsed current plating at on-time/off-time ratio of 0.25, the surface appearance of the alloys was similar to that obtained with direct current at the same alloy composition. Significant alteration of the current modulation in the pulsed plating resulted in a change in surface appearance, that is, the smoother deposit was obtained by increasing the pulse off-time. In the periodically reversed current plating at a given average cathodic current density, the rounded granular deposits were obtained, regardless of the pulse cycle and duty of anodic current pulse. The displacement reaction and a chemical or electrochemical dissolution of the deposited metals were estimated to bring about the changes in the surface appearance observed in these periodical electrodeposition by measuring the alloy composition, cathode current efficiency and the depositing potential of the alloys.
