Effect of P–Si Binary System on the Formation Mechanism of AZ91D MAO Coating

To enhance the corrosion resistance of magnesium alloy while improving its surface roughness to enhance organic bonding, the single pulse micro-arc oxidation treatment was conducted on magnesium alloy specimens for a duration of 1200 seconds. The treatment employed a mixed electrolyte of Na₃PO₄/Na₂SiO₃ with varying proportions, aiming primarily to investigate the treatment mechanism. Voltage–time response curves were recorded throughout the entire process. Characterization of the bioceramic films was achieved through the application of SEM, XRD, and XPS techniques, elucidating phase formation, surface morphologies, elemental distribution, and chemical valence. Subsequently, measurements were taken to assess the porosity of the film layer, alterations in thickness, roughness, and the kinetic potential polarization curves. The experimental findings reveal that P and Si elements influence the performance of AZ91D MAO coating by affecting cascading discharge and channel blockage. When the concentration ratio of PO₄³⁻/SiO₃²⁻ in the mixed electrolyte reached 0.02 mol L⁻¹/0.08 mol L⁻¹, the i_corr of MAO coating measured 4.6391 μA cm⁻², indicating better corrosion resistance.