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Corrosion is a major problem for the oil and gas industry, resulting in significant financial, environment and health losses. The protection of metals using corrosion inhibitors is an important topic that is becoming more and more important for researchers and industriel sector. Considering environmental and human health impacts, green corrosion inhibitors are more advantageous than traditional. The present work examined the effectiveness of Ascorbic acid, Olibanum and Trifolium repens as bio-inhibitors for corrosion of API5LX60 in a 3.5% NaCl,0.5 M sulfuric acid and naturel seawater. Inhibition efficiency, corrosion behaviour and the mechanism of the inhibitors on carbon steel are evaluated using gravimetry and electrochemical techniques (polarization for corrosion, electrochemical impedance spectrum (EIS), and open circuit potential). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examined the surface morphology. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR) and UV-Vis spectroscopy are employed to characterize the inhibitors. As a complementary method, Density Functional Theory (DFT) was used to investigate the fundamental corrosion inhibition mechanisms of different inhibitors compounds.
Olibanum, Ascorbic acid and Trifolium repens demonstrated significant corrosion inhibition properties, even at low concentrations. The electrochemical measurements validated that Olibanum,Trifolium repens was a mixed type inhibitors and Ascorbic acid work as an anodic inhibitors. The inhibition efficiency was reached the value of 84%, 75% and 97% in Olibanum,Ascorbic acid and Trifolium repens, respectively. Both in Olibanum andAscorbic acid physicochemical mechanism are responsible for the formation of a protective layer on API5LX60 surface to inhibit the electrochemical reactions.Trifolium repens present physical adsorption. Microscopic studies also confirm the formation of a protective layer of inhibitors on the steel surface .Optimized molecular structures inthe inhibitors molecules confirmed the inhibitive properties via DFT.
Keyword : Carbon steel, corrosion, green inhibitor, DFT, sulfuric acid, 3.5% NaCl, seawater.

Item Type	Thesis
Divisions	» Laboratory sciences and technical water and environment » Faculty of Science and Technology
ePrint ID	5444
Date Deposited	2025-06-23
Further Information	Google Scholar
URI	https://univ-soukahras.dz/en/publication/article/5444

@phdthesis{uniusa5444,
    title={Evaluation of the inhibiting power of some natural substances towards the corrosion of carbon steel in different environments.},
    author={Nour el Houda SOBHI},
    year={2025},
    school={University of souk ahras}
}