Experimental and theoretical study on the effectiveness of ionic liquids as corrosion inhibitors

An experimental and computational study, using a Density Functional Theory approach, was made about the anticorrosive effect of ionic liquids on hematite surfaces. Based on the hypothesis that adsorption is an initial step in the kinetics of corrosion, followed by electron transfer processes, adsorption energy calculations and corrosion rates are determined to investigate the effect as corrosion inhibitor of ionic liquids molecules. Several, potential descriptors of the inhibitor performance, conceptualized as an electrochemical process, based on the frontier orbital theory were used to characterize the interactions that might inhibit the corrosion, including the energies of the highest occupied (E-LUMO) and lowest unoccupied (E-HOMO) molecular orbitals, the energy gap between orbitals, crossed energies differences between HOMO and LUMO of the intervening chemical species and the surface, electronegativity (chi), hardness (eta), and number of transferred electrons (delta N). The main conclusion is that although the adsorption energy is a key parameter in establishing a correlation between calculated parameters and the experimental characterization of the ILs, the remaining chemical predictors also play an important role on the descriptions of activity corrosion, especially the electronegativity difference between surface and ILs, and the hardness of the IL.