Enhanced corrosion resistance and cell activity of magnesium alloy by DCPD/MgHPO4.3H2O coating via one-step chemical conversion

In order to solve the issue of rapid corrosion in magnesium alloy, composite coating of CaHPO4<middle dot>2H(2)O (DCPD) and MgHPO4<middle dot>3H(2)O were prepared in one step using chemical conversion method. By changing the pH of phosphating conversion solution, the composite coatings with varying contents of DCPD and MgHPO4<middle dot>3H(2)O were prepared, and their components were characterized. An electrochemical test was employed to compare the short-term corrosion properties of different composite coating. The findings revealed that the composite coating possessed the optimal short-term corrosion performance when pH of phosphating solution was 1.8. The long-term corrosion results demonstrated that the composite coatings fabricated at a pH of 1.8 in the phosphating solution, following a 7-days immersion, not only exhibited the optimal long-term corrosion resistance but also possessed the highest biomineralization capacity. This could be attributed to the fact that the composite coating prepared at this pH of phosphating solution possessed a structurally rational design, and MgHPO4<middle dot>3H(2)O could play a supportive role in maintaining structural integrity during the degradation process. Indirect cell culture results indicated that at a dilution concentration of 25 %, the cell activity of the coatings, except for Ca-Mg-P-3.0, was >75 %, suggesting good biocompatibility.