Investigation of the Structure and Self-Healing Performance of Composite Anion Intercalated LDH Coatings on Mg Alloy Surfaces

Based on the evaluation of sustained-release performance in aqueous solution, sodium dodecyl sulfate (SDS) and phosphate ions were selected as two anionic corrosion inhibitors with excellent inhibition properties. Using hydrothermal treatment, co-precipitation, and anion exchange techniques, LDH-P + S coatings containing both SDS and phosphate and MgAl-LDH coatings intercalated with silicate, phosphate, and SDS were successfully fabricated. The microstructure and composition of the various LDH coatings were characterized using XRD, FT-IR, XPS, SEM, and EDS. The corrosion resistance and durability of the LDH coatings were assessed using EIS, PDP, and hydrogen evolution tests. All four LDH coatings demonstrated good corrosion protection, with the LDH-P + S coating exhibiting slightly superior corrosion resistance compared with the others. Single-frequency EIS analysis was conducted to evaluate self-healing properties, indicating that the LDH-P + S coating performed the best in restoring protection. The superior self-healing behavior is primarily ascribed to the combined contribution of phosphate-induced passivation and SDS-mediated adsorption barrier formation.