Optimizing the ion-exchange time for enhanced corrosion resistance of ASP-intercalated MgAlCa-LDH Coating on Mg-Li alloy

Magnesium-lithium (Mg-Li) alloys are ultralight structural materials widely used in aerospace and defense applications; however, their practical utilization is limited by insufficient corrosion resistance. Layered double hydroxides (LDHs) have attracted significant attention as protective coatings for enhancing corrosion resistance. In this study, the effect of ion-exchange duration (3, 6, 9, and 12 h) on MgAlCa-LDH coatings intercalated with aspartic acid (ASP), an organic corrosion inhibitor, was systematically investigated. The coatings were synthesized on LA103Z Mg-Li alloy via a two-step hydrothermal method. The MgAlCa-LDH precursor was first grown at 90°C for 12 h, followed by ASP intercalation via an ion-exchange process at the selected durations (3, 6, 9, and 12 h) at 90°C. Among the coatings, the one synthesized with a 6 h ion-exchange exhibited a uniform and dense morphology, predominantly consisting of vertically aligned nanosheets, indicating superior structural compactness. Long-term immersion tests (216 h) demonstrated its excellent durability, with minimal pitting compared to the extensive damage observed in coatings prepared at other durations. Fourier transform infrared (FT-IR) spectroscopy confirmed the successful intercalation of ASP into the LDH interlayer, validating the efficacy of the ion-exchange process in enhancing corrosion protection.