Fabrication of high-performance graphene/nickel-cobalt composite coatings using ultrasonic-assisted pulse electrodeposition

This work developed a novel method to prepare graphene (Gr)/Ni-Co coating via using ultrasonic-assisted pulse electrodeposition method. The influences of ultrasonic on microstructure, distribution of Gr, surface roughness, microhardness, and electrochemical characteristics of the composite thin film were examined. It was demonstrated that ultrasonic wave can enhance the ion diffusion ability of the Gr/Ni-Co electroplating solution and enhanced the deposition rate, particularly for cobalt and Gr, resulting in increased surface roughness, an increased concentration of cobalt and Gr in Ni matrix, and a microhardness of 560 HV, 20% higher than stirring-pulse electrodeposition. Electrochemical behavior of the coating was investigated using EIS and polarization tests in 3.5% NaCl solution. By applying ultrasonic waves to the composite coating, corrosion resistance improved and corrosion rate was reduced from 0.01 mm/year to 0.007 mm/year. Co content in the deposit and uniform distribution of Gr nanosheets were both attributed to improved corrosion behavior.