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.