Abstract
The electrodeposition of Cu-Ni alloys from pyrophosphate bath containing thioglycolic acid (TGA) was investigated. Total metal concentration and that of pyrophosphate in the bath was kept constant at 0.1M and 0.3M, respectively. The alloy deposition was carried out under various conditions; TGA and nickel concentrations in the bath, and current density. The Cu-Ni alloy from a pyrophosphate bath had a single phase and uniform solid solution with a copper-rich composition, and its appearance was dull and mottling. An addition of TGA to the Cu-Ni pyrophosphate bath resulted in an increase in the nickel content in the alloy deposits all over the range of current density examined. The increment of the nickel content in alloy deposits was found to be about 5-25%. The Cu-Ni alloy obtained from TGA-containing bath had an uniform, smooth and bright surface, and a bright alloy deposits like nickel in appearance was obtained from a bath of lower copper concentration. Electron-microscopic examination of the Cu-Ni alloy deposit revealed that the addition of TGA to the bath brought about a formation of fine grain structure. The effect of TGA on the electrodeposition of Cu-Ni alloy might be explained in terms of the complexation of TGA with copper and nickel ions in the pyrophosphate bath.
