ELECTRODEPOSITION OF COBALT FROM AQUEOUS CHLORIDE SOLUTIONS

Electrodeposition of cobalt in aqueous chloride solutions has been studied by means of cyclic voltammetry and potentiostatic current-time transient techniques on rotating nickel disk electrodes. The electrocrystallization of cobalt is via a three-dimensional progressive nucleation and crystal growth mechanism under interfacial electron transfer/mass transfer control. As the deposition proceeds, concentration polarization becomes increasingly important after the nickel disk electrode is nearly or fully covered by cobalt crystallites. However, as the bulk concentration of Co2+ ions increases, the kinetics of the nucleation and crystal growth is increasingly dominated by interfacial electron transfer. It has also been found that in the electrodeposition process influenced by both interfacial/mass transfer processes, the electrode kinetics parameters can be obtained by analyzing the cathodic current responses of the reverse sweeps on the voltammetric curves. The measured Tafel slope of 29 mV and diffusion coefficient of 0.53 × 10−9 cm2 s−1 are in good agreement with the values reported in the literature. © 1990, The Electrochemical Society, Inc. All rights reserved.