Effect of thiourea during nickel electrodeposition from acidic sulfate solutions

Abstract

The effect of thiourea on the cathodic current efficiency (CE), deposit quality, crystallographic orientations, surface morphology, and polarization behavior of the cathode was investigated during nickel electrodeposition from acidic sulfate solutions for 2 hours at 60 degrees C. A slight decrease of 3 to 4 pet in the CE was observed, when the concentration of thiourea was increased from 2 to 40 mg dm(-3). The nickel deposit quality deteriorated significantly at higher thiourea concentrations; the surface morphology deteriorated and the contamination of the nickel deposits increased. The presence of thiourea affected the peak intensities of the crystal planes. Cyclic voltammetric studies on nickel deposition at 25 degrees C revealed depolarization behavior of the cathode at lower thiourea concentrations. <= 10 mg, dm(-3) ever, a mixed behavior is observed at higher thiourea concentrations. These changes were also observed Z, C in the exchange current density (i(0)) values.