Molecular-level insights into the corrosion protection mechanism of Mg/Al CO32--LDH films on steel in aqueous chloride environments

Despite their thickness of only a few microns, layered double hydroxide (LDH) films offer excellent corrosion protection for steel. However, the lack of molecular-level comprehension of this protective mechanism has hindered the optimal design of LDH films. Herein, we developed a molecular model of Mg/Al-CO32--LDH and investigated the nanoscale characteristics of water and ions in proximity to the LDH surface. Results underscore a robust attachment of water and ions to the LDH surface, accompanied by the attenuation of diffusion as they approach. The diffusion of interfacial water is predominantly influenced by H-bond interactions stemming from hydroxyl groups on the LDH surface. Additionally, the impediment of Cl- diffusion can be attributed to both anionic competition adsorption and the chemical bonding interactions of LDH.