Efficient and long-acting corrosion inhibition mechanisms and adsorption behavior of sodium laurate on AZ91D Mg alloy in oxalic acid solution

To address the severe corrosion of Mg alloys caused by oxalic acid generated by high-temperature oxidation in automotive engine coolant, this study employed electrochemical testing, surface characterizations, and theoretical calculations to investigate the corrosion inhibition performance, long-term protective mechanism, and adsorption behavior of sodium laurate (SL) on AZ91D Mg alloy in oxalic acid solution. The results indicated that the corrosion inhibition efficiency of 1 g/L SL reached 98.28% in oxalic acid solution, and excellent inhibition performance could still be maintained after 96 h immersion. The adsorption of SL followed the Langmuir adsorption isotherm model, and it could form a dense and stable hydrophobic protective film on the alloy surface. Theoretical calculations showed that SL molecules adsorbed on the alloy surface through a tilted configuration with carboxyl groups as active sites, forming a stable hydrophobic layer through synergistic physicochemical adsorption and effectively inhibiting the alloy corrosion.