Study on the overall performance of ZrO2 nanoparticle reinforced Co and CoP composite coating prepared by electrodeposition

Abstract

Co coating and CoP alloy coating reinforced by ZrO2 nanoparticles are prepared on the surface of the brass substrate by DC electrodeposition to improve the magnetic property and corrosion resistance. The Co/ZrO2 and CoP/ZrO2 composite coating electrodeposited on the surface of brass can be used in the field of thin-film magnetic heads, thin-film sensors and electronic circuits. By comparing the performance of different cobalt-based alloy coatings, the influence of ZrO2 nanoparticles on the electrodeposition and performance of Co coating and CoP alloy coating is studied. It is found that cobalt electrodeposition is a typical irreversible process with diffusion control. The CoP alloy coating comprises about 81% Co and 19% P. However, the electrodeposited CoP/ZrO2 composite coating possesses about 86% Co, 3% P, and 11% Zr. The incorporation of a 15 g/L ZrO2 nanoparticle with the size of 50 nm is beneficial to improve the cobalt content and decrease the amount of phosphorus in the CoP/ZrO2 composite coating. The hardness of CoP alloy coating is about 350 HV. However, the surface hardness of Co/ZrO2 and CoP/ZrO2 composite coating is about 400 HV and 470 HV, respectively. All the cobalt-based coatings show cellular surface morphology. The ZrO2 nanoparticles incorporated in the cobalt coating can enter into the cobalt lattice or disperse at the grain boundary to refine the grain size and limit the displacement of magnetic domain to improve the corrosion resistance and coercivity extremely. It is found out that the electrodeposited CoP/ZrO2 composite coating has the best corrosion resistance with only 9.7 μA/cm2 corrosion current density and the largest coercivity of 665.1 Oe. The optimal corrosion resistance and good magnetic performance of prepared CoP/ZrO2 is a promising material in the field of microelectromechanical systems as micro pumps, magnetic read heads, micro motors, and so on.