Influence of Current Density and Copper Ion Concentration on Properties of Electrodeposited Cu-Ni Coatings

Abstract:

A straightforward, highly effective, and environmentally friendly technique was investigated for protecting carbon steel surfaces from corrosion, i. e., depositing Cu-Ni alloy coatings on the workpiece's surface to impede corrosive medium. The effects of current density and copper ion concentration (Cu²⁺) on the composition, morphology, and properties of the coating were analyzed using scanning electron microscope, X-ray energy dispersive spectrometer, Vickers hardness tester, friction and wear tester, and electrochemical testing. Results show that a cauliflower-like Ni-rich protrusion structure appears on the coating surface. The lower current density and Cu²⁺ concentration affect the Vickers hardness and wear resistance of the coating by altering the microstructure and Cu/Ni content, both leading to a decrease in hardness and wear resistance. When the current density is 10 mA·cm^-2 and the Cu²⁺ concentration is 0.1 mol·L^-1, the corrosion current density of the deposited sample reaches 1.389×10^-5 A·cm^-2, and its surface corrosion damage is reduced compared to the uncoated sample after 24 h of salt spray test. Research on the deposition mechanism indicates that Cu²⁺ undergoes instantaneous nucleation under diffusion control, tending to grow vertically and form cauliflower-like protrusions, while Ni²⁺ is discharged uniformly across the surface under electrochemical control.