Abstract
Heavy electrodeposition of silver from conventionally concentrated cyanide baths was studied in terms of bath composition, the range of appropriate current densities and cathodic polarization curves.
It was found that the orientation indexes of silver deposits approached unity when the molarity ratio of KCN to AgCN was 5, and the appropriate range of potassium carbonate concentration varied with the molarity ratio of KCN to AgCN. Both potassium hydroxide and potassium carbonate must be added to baths for heavy silver electrodeposition. The appropriate range of potassium carbonate concentration increased with increases in the concentration of potassium hydroxide. Cathodic polarization also increased with increases in the concentration of potassium carbonate, but changed little with the addition of potassium hydroxide. The recommended conditions for heavy electrodeposition of silver in cyanide solutions with conventional concentration are AgCN: 40g/L, KCN: 98-107g/L, K2CO3: 10-70g/L, KOH: 10-40g/L at current density of not more than 1.8/dm2.
