Electroplating of cobalt from aqueous citrate baths

Electroplating of cobalt onto steel substrates from citrate baths has been investigated under different conditions of bath composition, current densit y, pH and temperature. A detailed study has been made of the influence of t hese variables on the potentiodynamic cathodic polarization curves, cathodi c current efficiency and the throwing power as well as the throwing index o f these baths. The optimum bath composition has been established and it con tains: CoSO4. 7H(2)O (0.36 mol dm(-3)) trisodium citrate (0.19 mol dm(-3)) and citric acid (0.1 mol dm(-3)) at pH 5.0. The microhardness of cobalt ele ctrodeposited from citrate baths is high and it may be, under certain condi tions, two or three times higher than that reported for cobalt electrodepos ited from other different baths. The surface morphology of the as-plated co balt was investigated by using scanning electron microscopy (SEM) while the structure was studied by using X-ray diffraction analysis and anodic strip ping voltammetry (ASV) techniques. (C) 1998 Society of Chemical Industry.