Electrodeposition of Ni-Co alloys from sulfamate baths

Abstract

The paper describes the results of electrochemical investigations of Ni‐Co deposition from a sulfamate bath in the presence of boric acid and two additives. The individual deposition of nickel was shown to be partly inhibited by the adsorption of sulfamate ions at low polarization; such inhibition was not observed for cobalt. The introduction of saccharin at 100 ppm, with a wetting agent seems to hinder sulfamate adsorption and Ni deposition departs at less cathodic potentials. The presence of cobalt has no eAect on nickel deposition, whereas cobalt deposition is hindered by the presence of nickel in the bath. Galvanostatic deposition was carried out at the surface of a RDE and with a rotating cylinder Hull cell. At low current densities deposits with a Co content of approx. 40% were produced, but this content was shown to decrease with the applied current density. Examination of experimental data showed that cobalt deposition is diAusion-controlled and that Co content decreases with the applied current density relative to the limiting current density.