Mechanistic studies of the influence of halogen substituents on the corrosion inhibitive efficiency of selected imidazole molecules: A synergistic computational and experimental approach

Adsorption behavior and corrosion inhibition mechanism of imidazole and its C2-halogenated analogues (with the halogen atoms being Cl, Br or I) on Fe(1 0 0) surface were investigated by DFT periodic slab calculations and electrochemical techniques. DFT calculations revealed that C2-halogenated imidazoles adopt the tilted conformation on Fe surface with a significantly lengthened C–halogen bond and readily undergo facile dissociation at the halo-substitution with calculated adsorption energies −3.95, −3.76 and −3.48 eV for 2-I-Imz, 2-Br-Imz and 2-Cl-Imz, respectively. Electrochemical evaluations supported with surface characterization studies showed that the inhibitor molecules adsorb onto mild steel with 2-I-Imz having the highest inhibition efficiency of 83.5%. The trend of observed inhibition efficiencies correlates with adsorption energies and kinetic behavior predicted by the MD approach. The strength of adsorption in the order I > Br > Cl. The present study therefore provides a thorough mechanistic understanding of the role halogen substituents could play on the corrosion inhibitive performance of small organic systems.