Control of Ni-P and Co-P Chemical Deposition with Transient Voltage Curves and Structure of the Deposits

Summary

Aqueous chemical deposition (ACD) of Ni-P and Co-P films can be controlled with a secondary current pulse (SCP) technique, measuring the voltage variation at an electrode on which electrodeposition is already occurring at constant current density as a consequence of short square current pulses, in the ms range. The transient voltage curves are interpreted and three parameters obtained: the transient Tafelslope, related to metal ion electrochemical discharge mechanism, the surface adsorption capacity and the surface ohmic resistance. The influence of H₂ or 02 saturation in the bath on the deposition kinetics and on the structure of thin layers is shown, and the mechanism of bath stabilization by several additives is interpreted.