Density functional theory and molecular dynamics analysis of oxadiazole derivatives as corrosion inhibitors in hydrochloric acid media (HCl)

In this study, we investigated the corrosion inhibition mechanisms of three newly identified oxadiazole derivatives in a hydrochloric acid (HCl) medium for mild steel. A range of computational approaches, including three semi-empirical methods, Hartree–Fock (HF), and density functional theory (DFT), were employed to identify the most suitable method for analyzing these derivatives. Among these approaches, DFT at the B3LYP/6-31G(d,p) level was determined to be the most appropriate. Solvent effects were incorporated using the self-consistent reaction field (SCRF) with the polarizable continuum model (PCM). Key quantum chemical reactivity descriptors, such as E_HOMO, E_LUMO, energy gap, electronegativity (χ), and hardness (η), were calculated to assess molecular reactivity on both global and local scales. Molecular dynamics (MD) simulations were also performed on the iron (110) surface to explore the adsorption behavior of the inhibitors. Results indicate that the inhibitor 6-MMOPP exhibits superior surface coverage and corrosion inhibition performance compared to 5-MOPP and 4-BPOMP. Additionally, Fukui function analysis suggests that the primary adsorption site for the 4-BPOMP inhibitor is the bromine atom. The theoretical findings strongly agree with experimental data, highlighting 6-MMOPP as the most effective corrosion inhibitor among the compounds studied.

Graphical abstract