Effect of CeO2 addition on pack cementation zinc coatings on Mg–4Y–4Al magnesium alloy

Abstract

Zinc coatings on as-cast Mg–4Y–4Al magnesium alloy were prepared by the zinc packed powder diffusion coating treatment, and the effect of CeO2 addition in the zincizing agent on the microstructure and electrochemical properties of the zinc coatings was investigated by OM, XRD, SEM, EDS and electrochemical workstation. The experimental results reveal that the microstructure of the zinc coatings is that the primary block α-Mg solid solution distributes on the continuous eutectic matrix composed of MgZn and intergranular α-Mg solid solution. The addition of CeO2 can increase the diffusion efficiency of Zn atoms into the alloy substrate. The thickness, compactness and corrosion resistance of zinc coatings increased first and then decreased with the increase of CeO2 addition from 0 to 9%. When the CeO2 content is 3%, the zinc coating gets the maximum thickness (about 1200 μm), and the corrosion current density reduced one order of magnitude than that of the substrate.