Hydroxyapatite/tannic acid coating (HA/TA) were prepared on AZ31 magnesium alloys (AZ31) via chemical conversion and biomimetic methods. The characterization and properties of the coating were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), corrosion testing, MC3T3-E1 cell proliferation assay, and MC3T3-E1 cell morphology observation. The results showed that tannic acid as an inducer increased the number of nucleation centers of hydroxyapatite and rendered the morphology more uniform. Compared to bare AZ31 magnesium (Mg) alloys (E corr = −1.462 ± 0.006 V, I corr = (4.8978 ± 0.2455) × 10 −6 A/cm 2 ), the corrosion current density of the HA/TA-coated magnesium alloys ((5.6494 ± 0.3187) × 10 −8 A/cm 2 ) decreased two orders of magnitude, and the corrosion potential of the HA/TA-coated Mg alloys (E corr = −1.304 ± 0.006 V) increased by about 158 mV. This indicated that the HA/TA coating was effectively protecting the AZ31 against corrosion in simulated body fluid (SBF). Cell proliferation assays and cell morphology observations results showed that the HA/TA coating was not toxic to the MC3T3-E1 cells.

In this work, one coating is comprised of ZrO 2 and the other consists of MgO as main phase composition was produced on AZ31 magnesium alloy using one-step plasma electrolytic oxidation (PEO). The purpose of this work was to study the corrosion resistance and cytocompatibility of the above-coated AZ31 magnesium alloys in order to provide a basis for AZ31 Mg alloy's clinical applications of biomedical use. The morphology and phase composition of the coatings were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion properties were examined using electrochemical testing, hydrogen evolution measurements, and immersion tests in a simulated body fluid (SBF). Compared with bare magnesium and the MgO coating, the ZrO 2 -containing coating exhibited an improved corrosion resistance. Cell proliferation assays and cell morphology observations showed that the ZrO 2 -containing coating was not toxic to the L-929 cells. The ZrO 2 coating was much denser and more homogeneous than the MgO coating, hence the corrosion resistance of the ZrO 2 -coated AZ31 Mg alloy was superior and more stable than the MgO-coated AZ31 Mg alloy, and ZrO 2 /AZ31 did not induce a cytotoxic reaction to L-929 cells and promote cell growth.