Research on the corrosion protection of in-situ prepared LiAl layered double hydroxides on AZ31 Mg alloy under standard atmospheric pressure and low temperature

Abstract

This work successfully prepared LiAl LDHs coatings on AZ31 Mg alloy under standard atmospheric pressure and low temperature. The whole process did not require a hydrothermal autoclave reactor and high pressure. Electrochemical test results showed that the coating was able to provide good corrosion protection performance. The LiAl LDHs coatings provided a large low-frequency impedance on AZ31. When the treatment time was 24 h, the maximum |Z|_0.01Hz at pH = 12 was 5.14 × 10⁴ Ω∙cm², which is more than an order of magnitude higher than the |Z|_0.01Hz of 1.81 × 10³ Ω∙cm² for the bare sample. Under the same treatment conditions, the potentiodynamic polarization test results showed that the LiAl LDHs coated samples had a lower corrosion current density and a higher breakdown potential. The i_corr was 1.78 × 10⁻⁷ A/cm² and E_br was −0.82 V_SCE compared to the Mg substrate (i_corr of 1.13 × 10⁻⁵ A/cm² and E_br of −1.53 V_SCE). Additionally, LiAl LDHs coatings also had a significant inhibitory effect on cathodic hydrogen evolution, providing targeted protection to the cathodic areas.