Gravimetric and quantum chemical studies of 1-[4-acetyl-2-(4-chlorophenyl)quinoxalin-1(4H)-yl] acetone as corrosion inhibitor for carbon steel in hydrochloric acid solution

1-[4-acetyl-2-(4-chlorophenyl)quinoxalin-1(4H)-yl] acetone (Q2) was examined as a corrosion inhibitor for carbon steel in 1. 0 M HCl by using weight loss measurements and the quantum chemical studies using density functional theory (DFT) methods. The percentage inhibition efficiency (η), was found to increase with increase of the inhibitor concentration due to the adsorption of the inhibitor molecules on the metal surface. In addition it was established the adsorption follows Langmuir adsorption isotherm. Moreover some thermodynamic data were calculated and discussed. Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE) and dipole moment (μ), the softness (σ), the fraction of the electrons transferred from the inhibitor to the metal surface (ΔN) and the total energy (TE) have been calculated for this compound. It was found that theoretical data support the experimental results.