Electrochemical and Spectroscopic Studies of the Influence of Thiourea on Copper Deposition from Acid Sulphate Solution

Abstract

SummaryThe effect of thiourea (TU, CS(NH2)2) on the charge transfer controlled and mixed controlled kinetics of copper deposition, from an acid sulphate electrolyte, has been studied via steady state current vs. potential curves at a rotating disc electrode. Pure charge transfer data are extracted and thiourea addition is shown to result in a complex relationship between the exchange current density for copper deposition and the additive concentration. This behaviour can be contrasted with that shown by two other additives, benzotriazole (BTA, C6H5N3) and 4,5-dithiaoctane-1,8-disulphonic acid (DTODSA, (HO3SCH2CH2CH2S-)2). Values of the product of mass transport coefficient and active electrode area (kmA) during cupric ion decay studies at a rotating cylinder electrode have been shown to be dependeht on the electrode potential and on the concentration of TU. Limiting current studies have indicated a potential-dependent adsorption of TU at the electrode surface. In-situ FTIR spectroscopic studies have confirmed the potential-dependent nature of the adsorption of TU at a copper electrode and have also shown that the co-ordination to the metal surface is via the sulphur atom.