Electrodeposition of Ni-Cd Alloys from Sulfate Bath

Abstract

The effects of composition and concentration of sulfate bath on the cathodic polarization curves and on the internal stress of Ni-Cd electrodeposit have been investigated. Limiting current density (l.c.d.) for Cd²⁺ deposition is influenced by Ni²⁺ discharge, if [Cd²⁺]/[Ni²⁺]>12×10^-2. In the bath concentration range where Ni²⁺ discharge has no influence on l.c.d. of Cd²⁺, the internal stress of electrodeposited alloys shows deflection of expansion, which is a typical property of Cd. In the concentration range where Ni²⁺ discharge has an influence on l.c.d. of Cd²⁺, on the other hand, the internal stress of electrodeposited alloys shows deflection of contraction, which seems to be interpreted in terms of an interaction between Cd²⁺ and Ni²⁺. However, in the case that [Cd²⁺]/[Ni²⁺]=12×10^-2 the electrodeposited alloys show no deflection.