Theoretical modeling and experimental studies of Terebinth extracts as green corrosion inhibitor for iron in 3% NaCl medium

Abstract In this study, essential oils (EOs) obtained from twigs, leaves and fruits of Terebinth (Pistacia terebinthus L.) was characterized by GC/MS analysis. We tested these as green corrosion inhibitors for iron in the neutral chloride medium (3% NaCl), employing electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) curves and surface characterizations SEM, EDX, IR spectroscopy were carried out. The theoretical aspect was elaborated using molecular dynamics (MD) simulation and density functional theory (DFT). Analyses of the experimental results showed that the three main components in the EOs from the twigs, fruits and leaves of Terebinth are α-Pinene (32.65-50.58%), Limonene (6.88-15.07%), and α-Terpineol (2.50-5.15%) with quantitative variations. The fruit EO at a concentration of 3000 ppm is characterized by the best anticorrosive protective properties than the leaf and twig EO. Indeed, the optimum percentage of this EO required to achieve the maximum efficiency was found to be 86.4% at 3000 ppm. The surface investigation strategies (SEM-EDX and IR) further validated that the corrosion barrier happens because of the adsorption of the inhibitors over the iron/3% NaCl interface. Also, the outcomes of the theoretical approach supported all the experimental results by illustrating the similar trend of inhibition efficiencies of various inhibitors and revealed that Terebinth EOs could serve as an effective inhibitor of iron in 3% NaCl.