Effect of added cobalt ion on electro-deposition of copper from sulfate bath using graphite and Pb–Sb anodes

Abstract

Effect of added Co 2+(aq) on copper electro-deposition was studied using Pb–Sb and graphite anodes and a stainless steel cathode. The presence of added Co 2+(aq) in the electrolyte solution was found to decrease the anode and the cathode potentials. The optimum level of Co 2+(aq) concentration in the electrolyte, with respect to the maximum saving of power consumption was established. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were used to study the influence of added Co 2+(aq) on the anodic and the cathodic processes in a copper sulfate-sulfuric acid electrolyte. The oxygen-evolution potential is depolarised at lower current densities (≤ 150 A/m 2) and attains saturation at [Co 2+] o ≅ 600 ppm; whilst at higher current densities (≥ 300 A/m 2) it is depolarised with [Co 2+] o ≥ 300 ppm. The presence of Co 2+ promoted the deposit of a smoother and brighter copper cathode as measured by surface reflectivity. X-ray diffraction (XRD) showed that added Co 2+ changed the preferred crystal orientations of the copper deposits. Scanning electron microscopy (SEM) indicated that the surface morphology of the copper deposited in the presence of added Co 2+ has well-defined grains. Analysis of cathode copper deposits found negligible cobalt.