DFT theoretical study of 7-R-3methylquinoxalin-2(1H)-thiones (RH; CH3; Cl) as corrosion inhibitors in hydrochloric acid

Quantum chemical approach at B3LYP/6-31G(d,p) level of theory, was used to calculate some structural and electronic properties of three quinoxaline derivatives, recently reported as mild steel corrosion inhibitors in acidic media, to ascertain the correlation between their experimental inhibitive efficiencies and some of the computed parameters. The results of most of the global reactivity descriptors show that the experimental and theoretical studies agree well and confirm that Me-QS is a better inhibitor than QS and Cl-QS, respectively. In addition, the local reactivity, analyzed through Fukui functions, show that the sulphur atom will be the main adsorption site.

► A theoretical study of three quinoxaline derivatives.
► We try to explain their experimental mild steel corrosion inhibition efficiencies.
► The solvent effect was also depicted using the PCM model.
► Most of the global reactivity descriptors agree well with the experimental results.
► The results show that the sulphur atom is probably the main adsorption site.