Self-healing performance and corrosion resistance of novel CeO2-sealed MAO film on aluminum alloy

Abstract

The self-healing performance with the improved corrosion resistance of novel CeO2-sealed micro-arc oxide (MAO) film on Al alloy was studied in this work for the first time. There are three steps involved, including: (1) Preparing porous film by performing MAO treatment on Al alloy with the average thickness of ~15 μm; (2) loading corrosion inhibitor by soaking MAO sample in Ce(NO3)3 solution to fulfill micropores-sealing process; (3) evaluating the self-healing ability of the sealed MAO film in acidic, alkaline and neutral solutions by scratch tests. The experimental results indicated that the corrosion inhibitor was characterized to be CeO2 which can locally fill the micropores to seal the MAO film. The optimized CeO2-sealed MAO film owned the lower porosity and the improved the corrosion resistance, which can be testified from the corrosion current density (Icorr) decreased by 2 orders of magnitude compared with the MAO film. Furthermore, the micropores in the MAO film acted as microcontainers to hold corrosion inhibitor to make CeO2-sealed MAO film showed self-healing ability. In the acidic environment (pH = 2 (8 mL/L H2SO4 + 20 mL/L H2O2)), the novel CeO2-sealed film exhibited positive self-healing effect morphologically with improved corrosion test result, and the underlying self-healing mechanism was discussed in detail.