Molecular interaction and corrosion inhibition of benzophenone and its derivative on mild steel in 1 N HCl: Electrochemical, DFT and MD simulation studies

In this study, Benzophenone (BP) and 2-Aminobenzophenone (2-A.BP) were evaluated for the corrosion inhi-bition effect on mild steel in 1 N HCl solution with various temperatures ranging from 303 to 333 K using gravimetric analysis. Spectroscopic analysis, Potentiodynamic Polarization (PDP), Electrochemical Impedance Spectroscopy (EIS), and Atomic Force Microscopy (AFM) were used to investigate corrosion inhibition mecha-nism and surface morphology of the inhibited metal surface. The inhibition efficiency (IE) of the compound increased with an increase in the concentration of inhibitors from 160 to 280 ppm. The maximum inhibition efficiency of 2-A.BP and BP are 90 % and 78.75 % at an optimal concentration of 280 ppm at 303 K. Poten-tiodynamic polarization measurement indicates the inhibitor to be a mixed-type and predominantly anodic type inhibitors. The inhibitors were adsorbed onto the mild steel surface via physisorption. The adsorption of inhibitor appears to function through Langmuir adsorption isotherm more appropriately. Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDAX) analysis confirmed the adsorption of inhibitor molecules, thus protecting the steel surface from being directly exposed to acidic ions. The results of the UV-visible spectroscopy furnished evidence of iron/inhibitor interactions. The mechanism of corrosion inhibition was further disclosed in theoretical investigation using density functional theory (DFT) and molecular dynamics (MD) simulation. DFT analyses revealed that both BP and 2-A.BP interacted effectively by electron-sharing mechanism resulting an interfacial adsorption of BP and 2-A.BP on the Fe (110) surface. MD studies showed the binding energy of 2-A.BP is less than that of BP. This confirms that 2-A.BP acts more efficiently in its role as an inhibitor. As a consequence, the computational analysis provided substantial evidence for the experimental results.