Effect of oxidation time on the corrosion behavior of micro-arc oxidation produced AZ31 magnesium alloys in simulated body fluid

The electrochemical corrosion behavior of microarc oxidation (MAO) coatings produced at various oxidation times on AZ31 Mg alloys was studied in a simulated body fluid (SBF). The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to characterize the corrosion behavior. The influences of the MAO time on the microstructure and corrosion properties are discussed. The initial porosity of the MAO coating was evaluated by the potentiodynamic polarization method. Post-corrosion phase identification showed that hydroxyapatite (HA) was formed on the surface of the samples. The ratio of Ca/P in HA was determined by the X-ray Fluorescence (XRF) technique. A physical model of the corrosion process with equivalent circuits at different corrosion stages is proposed.

► The corrosion resistance of Mg alloys is enhanced by controlling MAO times.
► The hydroxyapatite (HA) is formed on the corroded sample surface.
► The Ca/P ratio in HA determined by XRF is very close to 1.67.
► Stimulating the samples in SBF is essential to predict the in-vivo bioactivity.
► A physical model of the corrosion process with equivalent circuits is proposed.