Abstract
The effects of zinc ions on the internal tensile stress in nickel deposits obtained from Watts-type baths were studied. The variations in the elastic deformation of the deposits was measured in situ using a resistance wire-type strain gauge placed on the reverse side of the copper electrode.
Zinc ions were adsorbed by nickel hydroxide formed on and close to the electrode surface during nickel electroplating and codeposited as zinc oxide with nickel in the deposits. However, at a potential of less noble than-102V (vs Ag/AgCl sat. KCl), a part of zinc ions was electrically reduced to metallic zinc and codeposited with zinc oxide in the deposits. The amount of zinc oxide included in the deposits increased with an increase in the concentration of zinc ions in the plating solutions. The internal tensile stress in the deposits increased with an increase in the amount of the included zinc oxide and the increased tensile stress caused many cracks on the surface of nickel deposits.
