Layer-By-Layer Growth of Organic Molecules Controlled by the Defective Inorganic Surface for Enhanced Corrosion Protection and Bioactivity Properties of Magnesium Alloy

Although Mg metal offers advantages such as a high strength-to-weight ratio, biocompatibility, low cost, and nontoxicity, fabricating coated Mg with high chemical stability and antibacterial activity remains a formidable challenge. To date, the problems of continuous corrosion caused by uncontrolled Mg electrodeposition and serious interfacial side reactions in aqueous solutions have remarkably slowed down the practical application of metallic Mg. To address these issues, we proposed a combination approach of interface–plasma electrolysis (I-PE) and layer-by-layer (LbL) deposition to fabricate a tannic acid (TA)–MgO hybrid coating on an Mg anode, in which the TA layer served as the blocking layer and porous MgO films had microdefects that triggered physical locking. LbL formation was initiated through the charge-transfer phenomenon between the defective porous surface and TA molecules in the presence of cross-linkers, such as 2,5-diamino-1,3,4-thiadiazole (DAT) and 2-amino-5-mercapto-1,3,4-thiadiazole (AMT), to induce LbL deposition, that is, the consecutive growth of multilayer molecular structures on 2D hybrid organic–inorganic materials. The prepared coating surprisingly exhibited highly exceptional anticorrosion properties (inhibition efficiency ~82% and corrosion rate ~1610 nA/cm²) and excellent antibacterial activity, which are attributed to the optimized crosslinking degree and compactness due to the interaction between the TA–AMT composite and the porous MgO film. Density functional theory (DFT) calculations were performed to understand the reaction process between the organic AMT layers and the porous inorganic surface by bonding, adsorption behavior, and energy.