Zinc Plating from Cyanide Baths Consisting of Zn(CN)2-NaCN-NaOH-H2O and of Zn(CN)2-KCN-KOH-H2O

Zinc plating from cyanide baths was studied. Experiments were performed mainly at 30°C and without agitation, using sodium baths and potassium baths. Results are as follows: With an increase in temperature, total Zn content and total OH content, and with a decrease in total CN content, the cathodic current efficiency at identical current density increased and cathodic polarization decreased. Higher current efficiency and lower cathodic polarization were obtained in potassium baths than in sodium baths. Anodic passivation was observed at lower current density in potassium baths than that in sodium baths. The specific conductivity increased with an increase in free alkali content, and 1.2-1.3 times higher value was obtained in potassium baths compared with corresponding sodium baths. In potassium baths, the range of current density for the lustrous deposit was more limited than in sodium baths. Throwing power was also discussed.