Corrosion Protection Behavior of Aluminate Ion-Loaded Layered Double Hydroxide Coating on AZ31 Magnesium Alloy

The corrosion inhibition properties of NaAlO₂ for Mg-3Al-1Zn (AZ31) was evaluated by immersion and polarization tests. Then, the effect of aluminate ion loading on the corrosion resistance of layered double hydroxide (LDH) coating was investigated for AZ31 alloy. Aluminate ion-loaded LDH (LDHAlO₂) was synthesized from hydrotalcite (LDHCO₃) and co-deposited with magnesium and aluminum double hydroxide on AZ31 by electrophoretic co-deposition. Polarization, electrochemical impedance (EI), and wet-dry cyclic corrosion tests were performed on LDHAlO₂- and LDHCO₃-coated specimens. Adding 10-50 mmol/L NaAlO₂ to 0.1 mol/L NaCl solution created a passive region and shifted the breakdown potential of AZ31 above -1.0 V (Ag/AgCl), demonstrating the corrosion inhibition performance of aluminate ions. While aluminate ion loading did not significantly improve corrosion protection in polarization and EI tests, it was more effective in wet-dry corrosion tests. LDHAlO₂-coated AZ31 showed less weight gain and fewer clusters of shallow micro-pits compared to numerous deeper pits on the entire surface of LDHCO₃-coated AZ31. Thus, the aluminate ion-loaded LDH coating appears promising for enhancing corrosion resistance in atmospheric conditions.