Formation of a green protective layer by symmetric imidazolium-based ionic liquids for metal corrosion inhibition: Interfacial adsorption and mechanistic insights

Ionic liquids (ILs) have gained attention as green corrosion inhibitors due to their design flexibility and tunability. In this study, two imidazolium-based ILs, BPDB and BADB, were synthesized and systematically evaluated for their corrosion inhibition performance in acid cleaning applications. First, Density Functional Theory (DFT) calculations were employed to predict inhibition efficiency, identifying nitrogen atoms as key adsorption sites. The lower adsorption energy of BADB suggested a stronger inhibition capacity, attributed to the introduction of amino substituents. Based on these theoretical predictions, electrochemical tests at 0.1 mM confirmed high inhibition efficiencies of 93.8 % for BPDB and 96.3 % for BADB, validating the superior performance of BADB. Experimental surface analysis further supported these findings, revealing that nitrogen-containing organic fragments were adsorbed onto the Fe surface. To gain deeper mechanistic insights, Ab Initio Molecular Dynamics (AIMD) simulations were conducted to investigate the dynamic bonding evolution. Coordination number analysis demonstrated that BADB molecules formed stable Fe-N-Fe bonds, ensuring robust and sustained adsorption on the metal surface. By integrating theoretical predictions, experimental validation, and molecular-scale simulations, this study provides a comprehensive understanding of IL-based corrosion inhibition mechanisms. The findings offer valuable guidance for designing high-performance, eco-friendly corrosion inhibitors for industrial acid cleaning applications.