Studies on the Behaviour of Thiourea in Bright Nickel Plating

Abstract

SummaryAn attempt has been made to discuss the various phenomena taking place at a nickel electrode during the deposition of bright nickel from a Watts bath containing different concentrations of thiourea. The potential, polarization and capacity measurements indicate that the decomposition products rather than thiourea itself are responsible for the increased polarization arid the decrease in capacity and so for the consequent inhibition. Spectrophotometric measurements in the ultra violet region indicate the presence of another absorption range, in addition to that corresponding to thiourea, for the solution of thiourea in a Watts bath. It remains to be confirmed, however, whether it corresponds to the nickel-thiourea complex or to the decomposition products of thiourea. Spectrophotometric measurements have also indicated that the consumption of thiourea at the cathode is greater than at the anode and the difference is still greater in the presence of oxygen.