Corrosion inhibition of the EtOH extract of Zygophyllum Fabago for carbon steel in 1M HCl

Natural extracts have found wide application in preserving metallic materials against corrosion. They are readily available, non-toxic, environmentally friendly, naturally degradable, highly effective and renewable. In this study, we used the EtOH extract of Zygophyllum Fabago (ZF) as a corrosion inhibitor for carbon steel in a molar hydrochloric acid solution. GC-MS analysis of the Zygophyllum Fabago oil extract revealed the presence of 18 compounds, of which vanillin (VN) was the main component at 27.78% by weight. The influence of ZF on corrosion inhibition was examined using electrochemical techniques such as open circuit potential (OCP), polarization curves (PC) and impedance spectroscopy (EIS), as well as scanning electron microscopy coupled to elemental analysis (SEM/EDX). The results show that ZF extract acts effectively as a mixed corrosion inhibitor, with cathodic activity predominating. Inhibition efficiency increased in proportion to inhibitor concentration and immersion time, reaching a rate of 87%. This protective effect can be explained by the formation of a protective layer on the steel surface. The adsorption of ZF on the steel surface follows the Langmuir isotherm, which is characterized by the formation of a protective layer on the steel surface. The adsorption of ZF on the steel surface follows the Langmuir isotherm, characterized by a physisorption mechanism. To confirm the experimental results, we carried out a theoretical study using Density Functional Theory (DFT) and Molecular Electrostatic Surface Potential (MESP), In order to have a clear understanding of the inhibition and adsorption mechanisms of various constituents of ZF on steel.