Synergistic enhancement of corrosion resistance and photocatalytic activity on AZ31 Mg alloy using chelating agent-infused layered double hydroxides over plasma electrolytic oxidation coatings

This study introduces a novel approach to enhance the functionality of AZ31 magnesium alloy by integrating plasma electrolytic oxidation (PEO) with layered double hydroxides (LDH), followed by strategic post-treatments using chelating agents. Chelating agents, including nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), and ethylenediaminetetraacetic acid (EDTA), were incorporated to modify the LDH structure, resulting in tailored coating morphology and functionality. Among the tested systems, the LDH-EDTA coating exhibited a unique sieve-like structure with well-defined crystalline flakes embedded in the matrix, enhancing crystallinity and structural integration. The superior chelation effect of EDTA led to more organized growth of LDH flakes, contributing to robust chemical stability and a compact coating that effectively sealed surface micropores. This morphology provided a total polarization resistance of 3.62 × 10⁸ Ω·cm², demonstrating robust corrosion resistance. Furthermore, the LDH-EDTA system achieved 99.12% degradation of indigo carmine within 15 min, showing exceptional photocatalytic performance. Density functional theory (DFT) simulations provided deeper insights into the strong molecular interactions between indigo carmine and the LDH-EDTA matrix, supporting the enhanced experimental photocatalytic activity and stability.