Ultra-low-power preparation of multilayer nanocrystalline NiCo binary alloy coating by electrochemical additive manufacturing

Using the principle of electrochemical additive manufacturing (ECAM), a nanocrystalline Ni Co binary alloy coating was prepared on the surface of the steel substrate. This study shows the pulse-shaped current-time curve of ECAM during the coating preparation process, and the nanocrystalline Ni Co coating has a regular multilayer structure. At the same time, the ECAM method can effectively limit the growth time of the crystal nucleus and prepare nanocrystalline Ni Co alloy coatings with ultra-low energy consumption (5.75 × 10 −3  W). Besides, as the content of Co in the coating increases, the Ni Co alloy coating changes from an FCC single-phase structure to an FCC + HCP multi-phase structure. Finally, through the performance test of the nanocrystalline Ni Co coating, it is concluded that as the content of Co in the coating increases, the hardness of the coating increases, and the coating surface has a certain degree of hydrophobicity (100°–114°). The electrochemical corrosion test shows that the Ni Co coating has better corrosion resistance than the steel substrate. As the content of Co in the coating increases, the corrosion current density of the Ni Co coating increases from 9 μA/cm 2 to 32 μA/cm 2 .