Electrodeposition of Ni-Co alloys from sulfamate baths

The paper describes the results of electrochemical investigations of Ni-Co deposition from a sulfamate bath in the presence of boric acid and two addi tives. The individual deposition of nickel was shown to be partly inhibited by the adsorption of sulfamate ions at low polarization; such inhibition w as not observed for cobalt. The introduction of saccharin at 100 ppm, with a wetting agent seems to hinder sulfamate adsorption and Ni deposition depa rts at less cathodic potentials. The presence of cobalt has no effect on ni ckel deposition, whereas cobalt deposition is hindered by the presence of n ickel 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 d eposits with a Co content of approx. 40% were produced, but this content wa s shown to decrease with the applied current density. Examination of experi mental data showed that cobalt deposition is diffusion-controlled and that Co content decreases with the applied current density relative to the limit ing current density.