Enhancement of corrosion resistance of LA103Z magnesium-lithium alloy by hydrothermally synthesised MgAlCa-LDH coating

This study fabricated ternary MgAlCa–LDH (Layered Double Hydroxides) coatings on LA103Z magnesium-lithium alloy substrates via a hydrothermal method using different Al³⁺:Ca²⁺ ratios. The microstructure, phase composition, and corrosion resistance of the coatings were systematically investigated. The results demonstrated that the coating prepared with an Al³⁺:Ca²⁺ ratio of 1:1 exhibited the greatest thickness (5.2 ± 0.2 μm), the densest structure, the highest content of Ca and Al elements, and was free of cracks and pores. XRD and FT-IR analyses confirmed the successful synthesis of LDH coatings under all ratio conditions, with the most distinct LDH characteristic peaks observed at the 1:1 ratio. The intercalated anions were identified as NO₃⁻, and the layered structure showed an octahedral configuration. Electrochemical tests indicated that the coating with a 1:1 ratio exhibited the highest charge transfer resistance (917.5 ohm cm²), the highest polarisation resistance (8.150 × 10³ ohm cm²), and the lowest self-corrosion current density (2.13 × 10⁻⁶ A cm⁻²). In the 216-hour hydrogen evolution test, this coating showed the lowest hydrogen evolution volume (7.8342 mL cm⁻²) and retained a substantial amount of the LDH phase after corrosion, demonstrating optimal long-term protective performance. An Al³⁺:Ca²⁺ ratio of 1:1 is identified as the optimum condition for preparing MgAlCa–LDH coatings, which significantly enhances the corrosion resistance of the magnesium-lithium alloy.