Microstructure, Corrosion Resistance and Bonding Strength of Calcium Phosphate Coatings Formed on Pure Magnesium by a Simple Immersion Method

Magnesium is the lightest structural metal with high specific strength, therefore the alloys are increasingly used in transportation industries and mobile devices [1,2]. However, their poor corrosion resistance restricts practical applications. To improve the corrosion resistance, surface modification is generally applied to the materials such as a chromate conversion coating [2]. The problem of the techniques is that the coating bath of the treatment contain heavy-metal ion which is harmful to the environment. Previously, our group succeeded in the formation of hydroxyapatite (HAp) coatings on pure magnesium and magnesium-based alloys by a simple immersion method using Ca-chelate compound and dihydrogen phosphate [3-6]. The HAp-coated magnesium showed high corrosion resistance in both 3.5 wt % sodiu