Electroplating of Cobalt from Aqueous Citrate Baths

Abstract

Electroplating of cobalt onto steel substrates from citrate baths has been investigated under di erent conditions of bath composition, current density, pH and temperature. A detailed study has been made of the inÑuence of these variables on the potentiodynamic cathodic polarization curves, cathodic current efficiency and the throwing power as well as the throwing index of these baths. The optimum bath composition has been established and it contains : CoSO (0É36 mol dm~3) trisodium citrate (0É19 mol dm~3) and citric 4 . 7H2O acid (0É1 mol dm~3) at pH 5É0. The microhardness of cobalt electrodeposited from citrate baths is high and it may be, under certain conditions, two or three times higher than that reported for cobalt electrodeposited from other di erent baths. The surface morphology of the as-plated cobalt was investigated by using scanning electron microscopy (SEM) while the structure was studied by using X-ray di raction analysis and anodic stripping voltammetry (ASV) techniques.