Mg matrix in situ composites were fabricated from Mg and ZnO powder by a spark plasma sintering method. The composition and microstructure of the sintered samples were characterized. Corrosion properties of fabricated composites were evaluated by immersion and by electrochemical tests using Hanks’ solution. The results showed that the formation of in situ products improved significantly the corrosion resistance of the fabricated composites compared with pure Mg; Mg-10 wt % ZnO composites especially exhibited the lowest corrosion rate. In addition, an energy-dispersive X-ray (EDX) analysis showed that calcium phosphate formed as a corrosion product on the surface of Mg-10 wt % ZnO composites, while Mg(OH)₂ appeared as a corrosion product on the surface of Mg-20 wt % ZnO composite. The findings suggested Mg-10 wt % ZnO composite as a potential candidate for temporary implant application.

The influences of Zn content and heat treatment on microstructure and corrosion behavior of Mg-xZn (x = 1 wt%, 3 wt%, 5 wt%, and 7 wt%) alloys were studied. (α-Mg+MgZn) eutectic cells and Zn-segregated regions were formed in the as-cast alloys. The Zn-rich phases acted as microcathodes in galvanic corrosion. Volume fraction of the Zn-rich phases increased with Zn content of the as-cast alloys, leading to a decrease in corrosion resistance. The corrosion rate of the as-cast alloys increased four times with an increase of the volume fraction of eutectic cell from 0.07 vol% of Mg-1Zn alloy to 2.18 vol% of Mg-5Zn alloy. The corrosion rate of Mg-7Zn alloy with 2.87 vol% eutectic cells was two times higher than that of Mg-5Zn alloy. The Zn-rich phases dissolved by the T4 treatment and only the T4-treated Mg-7Zn alloy obviously showed eutectic cells of 1.73 vol%. The polarization resistance (Rp) of the T4-treated Mg-1, 3, and 5Zn alloys was 2 to 10 times higher than that of the as-cast alloys. The T4-treated Mg-7Zn showed similar Rp to the as-cast Mg-5Zn alloy. Consequently, the volume fraction of Zn-rich phases dominated the corrosion resistance of Mg-xZn alloys.