In-situ fabrication of durable corrosion-resistant ZrO2/Al2O3 coating on 3D-printed AlSi10Mg via two-step micro-arc oxidation

To enhance the long-term corrosion resistance of 3D-printed AlSi10Mg alloy, this work designed a two-step micro-arc oxidation (MAO) strategy. Given the difficulty of triggering micro-arc discharge in high-Si Al alloys, an intermediate transition layer was first prepared through one-step MAO in a silicate electrolyte. Subsequently, a two-step MAO treatment was performed in a phosphate electrolyte with the addition of K 2 ZrF 6 to seal the ablation holes formed during the one-step MAO process, achieving a self-sealing effect of the MAO coating. Ultimately, a dense ZrO 2 /Al 2 O 3 ceramic coating with Si-W-Zr-P gradient distribution was obtained on the AlSi10Mg surface after the two-step MAO. Electrochemical tests reveal that the two-step MAO coating exhibits exceptional corrosion resistance, with a remarkably low corrosion current density (I corr ) of 3.42 × 10 −9 A·cm −2 , along with a protective efficiency (η p ) of up to 99.8 %. Moreover, no obvious macroscopic corrosion signs are observed on the ZrO 2 /Al 2 O 3 coating after prolonged immersion, and its I corr remains stable at 9.26 × 10 −9 A·cm −2 , indicating durable protective performance. This study offers a novel and controllable strategy for the design of anti-corrosive coatings on 3D-printed high-Si Al alloys.