Corrosion behavior of Mg-Ca-Zn alloys with high Zn content

In this paper, the corrosion behavior of Mg-Ca-Zn alloys with high Zn content is investigated by electrochemical test and immersion test. The results show that the type, volume fraction and distribution of the second phases in Mg-Ca-Zn alloys change with the increase of Zn addition. The corrosion resistance of Mg-Ca-Zn alloys increases initially, followed by a decrease, but then again increases with the addition of Zn content. The corrosion resistance of XZ12 alloy is the best among the four alloys and the corrosion rates by weight loss of it is about 2.47 mm/y. For XZ10 alloy, Mg2Ca phase is preferred to be corroded to form a corrosion channel to accelerate the corrosion. While in XZ12 alloy, higher corrosion resistance of Mg2Ca enriched with Zn becomes the key to reduce the corrosion and thus induces uniform corrosion. The intermittent ternary phase in XZ15 alloy acts as the cathode for accelerating corrosion, while the continuous reticular ternary phase in XZ18 alloy serves as a barrier for further corrosion.