抄録
The throwing power of cyanide baths for silver plating was studied with respect to composition and conductance of the baths and current density-cathode potential curves; and the range of appropriate current density was studied by Hull Cell Test.
The results obtained were as follows.
The increase in silver concentration or decrease in free potassium cyanide made cathode potential more base for the deposition of silver. This fact would be due to the behavior for keeping low silver concentration by inhibiting the dissociation of complex ions. However, when the concentration of silver was 30g/l or lower, the current density was beyond the range of fine crystal deposition so that the deposit was powdered.
The addition of potassium carbonate made bath conductance higher and also made throwing power higher. However, when its concentration was 90g/l or higher, the range of appropriate current density was made narrower by the appearance of burnt deposits.
The range of bath composition for high throwing power and appropriate current density was as follows:
Ag 30-50g/l
Free KCN 40-70l
K2CO3 30-60l
