Eco-inspired imidazolium lignin-based ionic liquids for iron corrosion Inhibition: An integrated theoretical perspective

Developing environmentally benign corrosion inhibitors for iron remains pivotal for both industrial efficiency and environmental sustainability. Herein, a multiscale computational approach was employed to evaluate the corrosion inhibition properties of three lignin-based ionic liquids on iron. By integrating density functional theory (DFT), Conductor-like Screening Model for Real Solvents (COSMO-RS), molecular dynamics (MD), and Self-Consistent Charge Density Functional Tight-Binding (SCC-DFTB) simulations, a comprehensive view of the electronic, solvation, and interfacial properties of 3-Ethyl-1-methyl-1H-imidazole-3-ium gallate (GAL-IL), syringate (SYR-IL), and vanillate (VAN-IL) was accomplished. DFT results revealed that SYR-IL features a narrower energy gap (2.86 eV) and higher electron affinity (1.76 eV) than its counterparts, suggesting enhanced reactivity. COSMO-RS analyses highlighted robust hydrogen-bond acceptor regions around the carboxylate moieties, contributing to favorable solvation. Molecular dynamics simulations depicted stable interfacial arrangements of the ILs in water, supporting surface coverage and reduced metal exposure. SCC-DFTB calculations confirmed strong chemisorption, with SYR-IL exhibiting the most negative adsorption energy (−3.66 eV) due to its multiple Fe–O and Fe–C bonds. These findings collectively underscore the potential of structurally tailored lignin-based ionic liquids to form protective, electron-rich barriers on iron surfaces, paving the way for environmentally benign, high-performance corrosion inhibitors.