Electrochemical behavior of electrodeposited Ni-WC composite coatings

The electrochemical behavior of Ni-WC composite coatings on mild steel substrate has been evaluated. WC particles of average size 5 gin were co-deposited with Ni on a mild steel substrate using a Watts bath at 50 degreesC. The effect of plating variables on deposition behavior was studied. The weight percentage of WC in the deposited layer decreased and plating efficiency increased with increasing current density from 0.1 to 0.3 A/cm(2). The potentiodynamic polarization behavior of Ni-WC coating samples was compared with that of pure Ni in freelyaerated 0.1 mol/l sulfuric acid solution. The passive current density increased and the passivity range decreased for the composite coatings as compared to pure Ni. The amount of WC in the coating did not exert any significant influence on the polarization behavior. The poor passivation properties of the Ni-WC coatings have been attributed to the presence of carbides in the coating. (C) 2004 Elsevier B.V. All rights reserved.