RELATION BETWEEN PLATING OVERPOTENTIAL AND POROSITY OF THIN NICKEL ELECTROLYTIC COATINGS

The relation between plating overpotential and porosity of thin nickel electrolytic coatings (0.2-mu-m) was investigated. The porosity of nickel coatings was shown to be dependent on coating structure, which is determined by the plating overpotential. A lower porosity can be achieved by using a relatively high plating overpotential resulting in the deposition of nickel coatings with fine grains. A relation between the through-coating porosity of thin nickel coatings and the activation overpotential was identified. At plating current densities approaching the limiting current density, the porosity tends to increase due to a mass transport effect on the coating thickness distribution along the substrate surface.