Ceratonia Siliqua L seeds extract as eco-friendly corrosion inhibitor for carbon steel in 1M HCl: Characterization, electrochemical, surface analysis, and theoretical studies

Abstract Electrochemical and theoretical behaviors of the carbon steel was investigated in 1M HCl solution using the Ceratonia Siliqua L seeds (CFE) extract. This extract was analyzed using GC-MS technique; it was found that the extract contains 18 compounds on which the main constituents represent 27.78 wt.% vanillin (VN), 25.69 wt.% α-tumerone (AT), 11.68 wt.% 2-heptanal (HP), 9.49 wt.% mome-inositol (MI), 4.94 wt.% 1-dotiacontanol(DT), and 2.92 wt.% linoleic acid (LA). The corrosion inhibition and adsorption (CIA) behavior were investigated using the electrochemical measurements (open circuit potential (OCP), polarization curves (PC) and impedance spectroscopy (IS)), and both thermodynamic and kinetic parameters (ΔHa, ΔSa and Ea). The outcomes show that CFE extract exhibits a worthy anti-corrosion action with an inhibition efficiency (η%) of 95% at 100 mg/l at 298 °K. This result could be attributed probably to the adsorption of CFE extract matrix on carbon steel surface, and this was confirmed by surface visualization using SEM-EDS technique. The adsorption of CFE extract onto carbon steel surface is controlled by a Langmuir adsorption isotherm, which suggests that there are no interactions between molecules of the CFE during adsorption. The computational chemistry calculations by density functional theory (DFT), natural bond orbital (NBO), molecular electrostatic potential surface (MESP) and Metropolis Monte Carlo (MC) methods were performed to better understand the inhibition and adsorption behavior of the main constituents of CFE extract on the Fe (110) surface.