Formation mechanism of electroless plating nickel-based composite coating on highly active rare earth magnesium alloys and its corrosion resistance and adhesion performance

Abstract

The process of preparing anodic oxide film containing active sites and electroless nickel plating on highly active rare earth magnesium alloy was developed. The formation mechanism of electroless nickel plating on active anodic oxide film and the structure and properties of the composite coating were studied by several surface and electrochemical techniques. The results showed that Ag nanograins with an average size of 10 nm were embedded into the anodic oxide film with pores of 0.1–2 µm. Ag nanoparticles provided a catalytic site for the deposition of Ni-B alloy, and the Ni crystal nucleus was first grown in horizontal mode and then in cylindrical mode. The corrosion potential of the composite coating increased by 1.37 V and the corrosion current reduced two orders of magnitude due to the subsequent deposition of Ni-P alloy. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different layers and the amorphous structure of the Ni-P alloy in the outer layer. These findings provide a new idea for electroless nickel plating on anodic oxide film.

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Central South University