Exploitation of a new green inhibitor against mild steel corrosion in HCl: Experimental, DFT and MD simulation approach

Abstract Origanum Compactum Benth Aqueous extract (OCAqE) have been analysed and investigated as green corrosion inhibitor for mild steel in acid solution (1 M HCl). The analysis of Origanum Compactum Benth Aqueous extract was performed using HPLC-UV-ELSD-MS. Electrochemical techniques, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), and mass loss were performed and showed that OCAqE is mixed type inhibitor and acts by adsorption on metal surface. OCAqE showed good inhibition efficiency of 92% at a concentration of 0.4 g/L. The adsorption mode of OCAqE on mild steel surface follow Langmuir isotherm. Surface analysis (SEM) of mild steel specimen has shown the decrease in surface deterioration after addition of OCAqE inhibitor to the HCl solution. Density functional theory (DFT) and Molecular dynamics (MD) have been introduced in order to carry out a more rigorous theoretical treatment of the inhibitive performance. The comparative study based on the low-energy electronic structures shown that the trend of inhibition potentials of the major compound of this extract depend on the effect of molecular structure on the electron donating/accepting ability.