Kinetic Characteristics of Electrodeposition of Ni-Co-Al2O3 Composite Coating

Abstract

The kinetic features of electrodeposition process of a wear-and corrosion-resistant composite electrochemical nickel-cobalt-aluminum oxide coating were investigated. Potentiodynamic studies showed that in the process of the CEC formation at the cathode the electrode polarization decreases, and the value of the limiting current density increases by more than twice. Consequently, the rate of the CEC electrodeposition process increases and the range of operating current densities expand in comparison with the control coating with the Ni-Co alloy. Temperature-kinetic, chronopotentiometric methods, values of the temperature coefficient of the reaction rate and the diffusion coefficients of nickel ions were used to determine the mechanism of CEC electrodeposition. As the result of determining the nature of limiting stage of the electrodeposition process of CEC nickel-cobalt-aluminum oxide, it was found that it is caused by such two coupled processes proceeding at comparable rates, as electrophoretic transfer of electroactive particles to the cathode and overgrowing of dispersed particles adsorbed on the cathode surface with electrodeposited metals.