Elucidating the corrosion inhibition mechanisms: A computational and statistical exploration of the molecular structure-efficiency relationship for phenolic Schiff bases in acidic medium on the mild steel surface

Abstract

This study investigated mild steel corrosion inhibition using four Schiff bases in a theoretical framework. The study used statistical analysis to relate the experimental inhibitor's efficacy to theoretical data, revealing the corrosion inhibition process. Density functional theory (DFT) was used to assess the global reactivity of the four inhibitors' neutral, protonated, and complex forms. Where, Fukui functions were used for local reactivity study of the four inhibitors in neutral and protonated forms. To study system dynamics at the inhibitor-steel contact, a Monte Carlo simulation was performed. The experimental and quantum results are strongly correlated when the global quantum features of the neutral and protonated forms, such as the dipole moment μ, EHOMO, and ELUMO, are examined. The PA and pKa protonation parameters demonstrate that the protonation of the compounds strongly influences the inhibition efficiency. According to Fukui functions, the amine function (N) is the highest nucleophilic reactivity, making it highly sensitive to electrophilic attack, for all four inhibitors. The stability and predominance of complex forms in the medium were interpreted using thermodynamic characteristics of PSBi-FeCl2 complexes. Monte Carlo simulation yielded the most stable adsorption configurations, which were geometrically and energetically examined to explain experimental data. QSAR shows a significant linearity between theoretical parameters and experimental inhibitory efficiency.