Effect of bath constituents and superimposed sinusoidal A.C. on nickel electroplating from acidic acetate solutions

Abstract

The electroplating of nickel from acidic acetate solutions containing 0.25 mol (CH 3COO) 2Ni·4H 2O l -1 with the stepwise inclusion of 0.3 mol H 3BO 3 l -1, 0.2 mol CH 3COOH l -1 and 0.1 mol CH 3COONa·3H 2O l -1 was investigated. Electroplating in the presence of 1 g gelatin l -1 and/or 1 g toluene-4-sulphonic acid l -1 as organic additives was also examined. The cathodic polarization and current efficiency for nickel electroplating were affected to different extents by the bath constituents. Structural studies with a scanning electron microscope proved that the most regular and coherent nickel plate was that obtained from the solution containing both of the organic additives. The operating conditions to obtain a mirror-bright nickel plate from this solution were j = 2 A dm -2, t = 10 min and pH 5.25 at 25 °C. It was found that sinusoidal a.c. superimposed on the direct plating current decreases both the cathodic polarization and current efficiency, but increases the brightness of the nickel plate.