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

• In situ doped zinc phosphate/cerium phosphate amorphous encapsulated nanocrystalline MAO mixed coating is prepared on LY12 alloy. • The co-doped MAO coating demonstrates excellent electrochemical corrosion resistance in salt solutions compared to aluminum substrates. • The co-doped MAO coating release Zn 2+ and Ce 3+ during the corrosion process and forms a mixed corrosion product to fill the corrosion micro-region. 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, Zn 2+ is released and deposited as corrosion products Zn(OH) 2 to cover weak corrosion micro-regions in the coating. Simultaneously, Ce 3+ 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.