Construction of a sandwich-like Gr/Ni composite coating on AZ91D magnesium alloy to achieve excellent corrosion and wear resistances in the seawater

Preventing AZ91D magnesium alloy from severely wear and corrosion should be of significance so as to extend its applications. In this work, we systemically investigated graphene (Gr) doping concentration to influence the structure and performance of Gr/Ni composite coatings on AZ91D Mg alloy in the seawater. The results showed that the optimal Gr doping Gr/Ni composite coating on Mg alloy could possess much higher hardness and better adhesive strength as well as much lower wear rate in the seawater. Moreover, the novel composite sandwich structure was utilized to construct multi-interfacial Gr/Ni composite coating on AZ91D Mg alloy, which successfully achieved much more excellent long-term corrosion and wear resistances in the marine. Density functional theory calculations clarified the mechanism of sequential adsorption of nickel to graphene, indicating that it easily gave rise to graphene agglomeration in electroplating process. However, the multi-interfaces could provide more stretching space for graphene sheets and reduce the folding tendency of graphene. These results indicated that the sandwich-like structure Gr/Ni composite coating brought excellent properties for AZ91D magnesium alloy to enhance its services in the marine and aviation environments. [Display omitted] •Series of electroplating Gr/Ni composite coatings were prepared on AZ91D Mg alloy.•Gr/Ni composite coating with optimal graphene could possess much better performances.•Sandwich-like Gr/Ni coating had excellent anti-corrosion and wear in the seawater.•Sandwich-like Gr/Ni composite coating could provide superior protection for AZ91D.