Theoretical Study of Khellin Derivatives as Corrosion Inhibitors Based on Density Functional Theory (DFT)

Theoretical studies of Khellin in the presence of electron donor and electron with-drawing groups as a corrosion inhibitor are investigated using the B3LYP/6-31G (d, p) theory level with Gaussian software. This research focuses on the correlation between corrosion inhibition efficiency (EI%) and quantum chemical parameters such as EHOMO (Highest Occupied Molecular Orbital Energy), ELUMO (Lowest Unoccupied Molecular Orbital Energy), energy gap (∆E), dipole moment (µ), absolute hardness (η), absolute softness (σ), the absolute electronegativity (χ), the fractions of electrons transferred from the inhibitor molecule to the metallic atom (∆N), the electrophilicity index (ω), total energy (ET) and theoretical corrosion inhibition efficiency (EI %). The generated results show that the electron-donating groups increase the corrosion inhibition efficiency of Khellin in the sequence -NH2> -SH> -H> -NCH2> -NO2. The highest corrosion inhibition efficiency obtained about 98.40% proves that NH2-Khellin is the best corrosion inhibitor of iron.