Prosopis juliflora pod and gum as green corrosion inhibitor - density functional theory approach

Plant extracts have emerged as promising corrosion inhibitors due to their eco-friendly nature as well as their adsorption ability on metals to form a protective barrier. The corrosion inhibition effect of seven major phytochemicals of Prosopis juliflora pods and gum (PJPG) was studied by density functional theory-based simulations through the hybrid functional B3LYP with the basis set of 6–311 G (d, p). The quantum chemical descriptors like HOMO, LUMO energies, energy gap, dipole moment, softness, hardness, and fraction of electron charge in geometrically optimized structures of the PJPG molecules have been calculated. A correlation between parameters and their inhibition efficiency revealed that quercetin, juliprosine, juliprosopine, and caffeic acid have active centers with a greater tendency to donate electrons to the metal and contribute to corrosion inhibition. Mulliken charges of the contributing atoms suggested a possible bonding with the metal. The values of the fraction of electron charge transfer (ΔN) of 0.304 and 0.369 for quercetin and juliprosopine molecules, respectively, suggested their favorable chelating ability for the metal. Monte Carlo results yielded the lowest adsorption energies of −49.476 kcal/mol for quercetin and −18.040 kcal/mol for prosopidione, indicating favorable adsorption of the inhibitor on the Fe (1 1 0) surface. Further, Fukui indices were used to ascertain the local reactivity of these molecules. The results affirmed that the selected PJPG phytochemicals are possible corrosion inhibitors for the Fe (1 1 0) surface.