Electrodeposition of cobalt from gluconate electrolyte

Cobalt electrodeposited onto steel substrate was carried out from solutions containing cobalt sulfate, boric acid and sodium gluconate. The study dealt with the influence of bath composition, current density, pH and temperature on the potentiodynamic cathodic polarization curves, cathodic current efficiency, and throwing power, as well as the throwing index of these baths. The microhardness of cobalt electrodeposited from gluconate baths is generally high and higher than that of cobalt deposited under similar conditions from sulfate, chloride, bromide and acetate baths. The surface morphology of the as-deposited cobalt was investigated using scanning electron microscopy (SEM) while the structure was studied using X-ray diffraction analysis. Cyclic voltammetric, as well as current-transient, techniques recorded on a glassy carbon electrode suggested that the deposition of cobalt from gluconate bath occurs via a nucleation process under charge transfer control.