Effect of zinc phosphate pretreatment on micro-arc oxidation performance

The integration of micro-arc oxidation (MAO) film and chemical conversion (PCC) technology is a promising surface treatment for magnesium alloys. In this study, a MAO treatment of PCC film layers in a Na2SiO3 electrolyte system was used. The composition, structure, corrosion resistance, and formation mechanism of composite films were thoroughly investigated and discussed. Results showed that the composite-coated samples could effectively retard the corrosion of magnesium alloy. Additionally, the MAO treatment of zinc phosphate PCC coatings led to a reduction in pore size and enhanced coating compactness. The electrochemical test results showed that the composite coating has a higher impedance modulus in the low-frequency region (|Z|MAO/PCC-5 (2.38 × 105 Ω cm2) >|Z|MAO (1.31 × 104 Ω cm2) >|Z|PCC-5 (1.54 × 103 Ω cm2) >|Z|AZ91D (2.08 × 102 Ω cm2)), which improves the corrosion resistance of both the single MAO coating and the PCC coating. Meanwhile, the introduction of zinc effectively improves the antimicrobial properties of the coatings. This study provides a new idea for the preparation of anticorrosive and antimicrobial composite coatings on light metal surfaces.