The adsorption mechanism and inhibition performance of three quinoxaline derivatives 3-methyl-2-phenyl quinoxaline (MPQ), 2,3-diphenyl quinoxaline (DPQ) and 3-methyl-2(3’-methoxy-4’-hydroxyphenyl)quinoxaline (MMHPQ) were investigated as corrosion inhibitors using Density functional theory(DFT) at the B3LYP/6- 31G(d,p) basis set level. Quantum chemical parameters most relevant to their potential action as corrosion inhibitors such as EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy gap(ΔE), hardness(η), Softness(S), dipole moment(μ), electron affinity(A), ionization potential(I), the absolute electronegativity (χ) , the fraction of electron transferred (ΔN), electrophilicity index(ω) and the back-donation(ΔE Back-donation) have been calculated. The local reactivity has been analysed through the Fukui and condensed softness indices in order to predict both the reactive centres and to know the possible sites of nucleophilic and electrophilic attacks. The theoretical conclusions were found to be consistent with the experimental data reported.
