Polydopamine functionalized graphitic carbon nitride nanosheets as acid stimuli-responsive nanocarrier of 2-mercaptobenzimidazole for intelligent anticorrosion coatings

Abstract

Waterborne epoxy (EP) is considered a promising environmentally friendly anticorrosive technology with extensive potential applications. However, its limited anticorrosive ability poses significant challenges in practical usage. In this study, we use dopamine (DA) polymerization to load 2-mercaptobenzimidazole (MBI) onto the surface of g-C₃N₄ (CN) nanosheets, resulting in the synthesis of MBI-PDA@g-C₃N₄ (MBI-PDA@CN) nanosheet composites. The MBI-PDA@CN composite exhibits favorable hydrophilicity and high loading capacity of 35.8 %, enabling the formation of compact bonding layer at the interface with the EP. Simultaneously, the MBI-PDA@CN nanosheets exhibit a fully lamellar structure, thereby effectively impeding the infiltration of corrosive agents. Electrochemical tests show that the coating resistance (R_p) of MBI-PDA@CN/EP coating (8.5 × 10⁷ Ω cm²) exhibited a significantly higher magnitude compared to that of the EP (2.6 × 10⁶ Ω cm²) after being immersed in 3.5 wt% NaCl solution for 30 days. It is worth mentioning that the MBI-PDA@CN nanosheets possess the capability to gradually release MBI-PDA molecules in acidic environments. Given that MBI and PDA function as outstanding metal corrosion inhibitors, they substantially augment the corrosion resistance of the coating in acidic conditions. This study presents an intriguing approach to fabricating robust corrosion-resistant composite coatings.