Enhancing corrosion resistance of MAO coatings on Al alloy LY12 through in situ co-doping with zinc phosphate and cerium phosphate

Corrosion of aluminum (Al) alloys during service limits many applications. Micro-arc oxidation (MAO) coatings can enhance corrosion resistance, but porous defects in the films undermine their effectiveness. Here, by mixing a phosphate electrolyte with soluble Zn and Ce salts, zinc phosphate and cerium phosphate co-doped MAO corrosion-resistant coating is prepared on Al alloy LY12. Zinc phosphate and cerium phosphate are incorporated in situ to form an amorphous encapsulated nanocrystalline structure. During long-term corrosion, Zn²⁺ is released and deposited as corrosion products Zn(OH)₂ to cover weak corrosion micro-regions in the coating. Simultaneously, Ce³⁺ released from MAO coating co-doped with zinc phosphate/cerium phosphate forms Zn(OH)₂/Ce(OH)₃ due to the small solubility product K_sp to further enhance corrosion resistance. Compared to pristine Al alloy, corrosion potential increases from -1.306 to -0.819 V_SCE, and corrosion current density decreases by 4 orders of magnitude from 2.6 × 10⁻⁶ to 2.5 × 10⁻¹⁰ A·cm⁻². Co-doped MAO coating significantly enhances corrosion resistance of Al alloy LY12 and shows great potential for a wide range of applications. © 2025 The Authors.