The role of pH on structure, corrosion behavior and biocompatibility of MgFe layered double hydroxide coating on Mg-Nd-Zn-Zr alloy.

In the present study, MgFe layered double hydroxide (LDHs) coatings were prepared on the surface of Mg-Nd-Zn-Zr (JDBM) alloy by a chemical conversion method, and the effects of the pH value (pH = 8, 10 and 12) of the prepared solution on the morphology, corrosion resistance and biocompatibility of the coatings were studied. The thickness of the Mg-Fe LDHs coatings was 43.79 ± 3.65 μm (pH = 8), 46.18 ± 1.05 μm (pH = 10) and 28.71 ± 4.05 μm (pH = 12), respectively. The corrosion rate of the JDBM matrix in simulated body fluid was 3.1 ± 0.1 mm/year, the LDHs coating significantly slowed down the corrosion process. When the pH of the mixed solution was 10, the Mg-Fe LDHs coatings exhibited the lowest corrosion rate (0.07 ± 0.008 mm/year). The cell experiment results indicate the Mg-Fe LDHs coating significantly enhances the cell viability of both EA.hy926 cells and A7r5 cells. At a 50% extract concentration, the cell viability for the JDBM alloy was 70% (EA.hy926) and 61% (A7r5), respectively, while the cell viability for the Mg-Fe LDHs coatings exceeded 95% for both EA.hy926 cells and A7r5 cells. In addition, the hemolysis ratio of the coated sample is about 1.7%, much lower than that of the JDBM alloy (46.7%), meeting the clinical requirements for medical materials with a hemolysis ratio below 5%. Based on the above results, the corrosion resistance and in vitro biocompatibilities of the JDBM alloy are significantly improved by the Mg-Fe LDHs coatings.