Comparative theoretical study on the corrosion inhibition properties of benzoxazole and benzothiazole

The electronic parameters of two azole molecules, namely benzoxazole (BOX) and benzothiazole (BTH), have been studied using DFT/B3LYP, MP2, and HF methods with the 6-31G (d, p) basis set. The quantum chemical properties/descriptors most relevant to their potential action as corrosion inhibitors have been calculated in the gas and aqueous phases for comparison. They include: total energy (T (E)), E (HOMO), E (LUMO), energy gap (Delta E), dipole moment (mu), hardness (eta), softness (sigma), electronegativity index (chi), fraction of electrons transferred (Delta N), total energy change (Delta E (T)), and electrophilicity (phi). The solvent effect on the studied parameters was found to be insignificant. Molecular dynamics simulation was also employed to search the most stable adsorption configurations of Fe(110)/azole system in a water environment. The binding, deformation, and non-bond interaction energies between corrosion inhibitors and Fe(110) surface were given. Finally, we deduced that BTH had better corrosion inhibition efficiency than BOX, which was in agreement with the general trend-the inhibition efficiencies of molecules containing heteroatoms is such that O < S.