First-principles prediction of corrosion inhibition efficiency for thiazole-based compounds on iron and aluminium protection using DFT and Monte Carlo simulation

This study combines density functional theory (DFT,B3LYP/6–311++G(d,p)) and Monte Carlo (MC) simulations for the first time to evaluate eight thiazole derivatives (T1–T8) as corrosion inhibitors on Al(111) surfaces. DFT calculations yielded electronic parameters HOMO–LUMO gap, electronegativity, hardness/softness, electrophilicity, and charge transfer in both gas phase and aqueous solution, while MC simulations using the COMPASSIII force field determined adsorption and deformation energies. Results show thiazole-2,4-diamine (T6; 4.828 eV) and thiazole-2,5-diamine (T7; 5.066 eV) have the smallest HOMO–LUMO gaps and most negative adsorption energies (−42.0 and −42.1 kcal/mol), about 25% stronger than T1, indicating superior electron-donating ability and more stable surface adsorption. Aqueous solvation further enhanced charge transfer and adsorption tendency, especially for T3 and T6. Overall, T6, bearing two NH2 groups, emerges as the most promising candidate for Al corrosion protection, and this work establishes a theoretical framework linking electronic structure, optical properties, and adsorption behaviour to guide future inhibitor design.