Performance of two new imidazoline derivatives as potential corrosion inhibitors for mild steel in 1.0 M HCl medium: Combining experimental and computational approaches

Two new heteroatomic aromatic compounds, namely, 3-(2-bromoethyl)-5,5-diphenylimidazolidine-2,4-dione (IMID-Br) and 5,5-diphenyl-3-(prop-2-yn-1-yl) imidazolidine-2,4-dione (IMID-CH), were synthesized from imidazolidine derivatives. Their chemical structures were characterized using proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR) techniques. After this, these compounds were evaluated as corrosion inhibitors for mild steel in a 1.0 M HCl solution, by using electrochemical methods, scanning electron microscopy (SEM), and computational theoretical studies employing DFT and molecular dynamics (MD) simulations. The potentiondynamic polarization (PP) curves indicated that these compounds act as mixed-type inhibitors. The electrochemical spectroscopic impedance (EIS) indicated that the inhibition corrosion process was controlled by a pure kinetic activation by the presence of one capacitive loop. The EIS results revealed that the studied compounds are effective corrosion inhibitors, with inhibition efficiency increases with concentration, reaching a maximum of 94.81 % and 89.3 % at 10-3 M for IMID-Br and IMID-CH, respectively. Furthermore, the SEM analysis shown that the IMID-Br and IMID-CH products prevent the dissolution of mild steel in a 1.0 M HCl solution by forming a protective layer on its surface. The effect of solution temperature indicated that these both compounds take their performance at high temperature. In the same, the obtained activation parameters indicated that the dissolution process of mild steel is endothermic and that the compounds act through physical adsorption on the metal surface, according to the Langmuir isotherm. Finally, theoretical studies using DFT calculations and MD simulations corroborated the experimental results and confirmed the obtained order of inhibition efficiency.