Mechanism study of composite co-deposited Cu/Co-Mo corrosion-resistant coating on 6061 Al alloy

To improve the bonding strength of the 6061 Al alloy with the plating layer and enhance the corrosion resistance, a Cu/Co-Mo corrosion-resistant plating layer was deposited on its surface. Through Scanning Electron Microscope, it is found that Cu/Co-Mo and the substrate can form an obvious three-layer composite structure, and X-ray diffraction detects that the CoMo coating is an alloy with obvious amorphous characteristics, and its phase composition is Co3Mo. After performance testing, the composite coating improved the corrosion resistance and hardness of the substrate and could play a good role in protecting the 6061 Al alloy. In addition, the mechanism of induced codeposition of CoMo alloy was investigated, and the deposition of Mo6+ was determined by cyclic voltammetry to be a three-step six-electron irreversible reduction reaction. Chronopotentiometry revealed that Mo6+ underwent a diffusion-controlled transient nucleation process. The AC impedance indicated that the selection of a suitable voltage is beneficial to reduce the hydrogen precipitation reactions during electrodeposition.