Effect of negative voltage on the microstructure, degradability and in vitro bioactivity of microarc oxidized coatings on ZK60 magnesium alloy

• Negative voltage influences the ions transferring in the oxidation process.
• Electrochemical corrosion resistance increases with increased negative voltage (0–100 V).
• Negative voltage has an effect on the controllability of MAO coating degradability in SBF.

Ceramic coatings were fabricated on ZK60 magnesium alloy by microarc oxidation (MAO) with different negative voltages. The coating degradability and bioactivity were evaluated by simulated body fluid (SBF) soaking test. A scanning electron microscope (SEM) and an X-ray diffractometer (XRD) were employed to characterize the coating morphology and phase composition. The electrochemical workstation was used to investigate the electrochemical corrosion properties of the samples. The results show that the coating growth mechanism can be influenced by the introduction and increase of negative voltage through affecting the direction and speed of ions transferring. With increase of negative voltage in the range of 0–100 V, the coating electrochemical corrosion property is improved, the coating degradation rate is reduced, and the combination property of coating corrosion resistance and apatites forming ability is enhanced.