Inhibitive effect of Thymus satureioides essential oil as a green corrosion inhibitor for mild steel in an acidic medium

• A. Boukhraz¹, A. Chaouik^2,3, R. Salghi³, H. Elhartiti¹, N. Saouide el ayne⁴, A. Zaher¹ and M. Ouhssine¹

¹ Laboratory of Agro-Physiology, Biotechnologies, Environment and Quality, Department of Biology, Faculty of Sciences, University Ibn Tofail, Kenitra, Morocco
² Laboratory of separation processes, Faculty of Science, University Ibn Tofail PO Box 242, Kenitra, Morocco
³ Laboratory of Applied Chemistry and Environment, ENSA, University Ibn Zohr, PO Box 1136, Agadir, Morocco
⁴ Laboratory of Electrical Engineering and Energy System, Faculty of Science, University Ibn Tofail, Kenitra, Morocco

Abstract: The efficiency of Thymus satureioides essential oil (EO) as inhibitor of mild steel corrosion in hydrochloric acid 1.0 M has been studied using polarization curves, electrochemical impedance spectroscopy (EIS) and weight loss measurements. The chemical composition of essential oil was characterized by 29 components, which accounted for 99.24% of the total oil. The major constituents were carvacrol (29.65%), followed by borneol (19.04%), linalool (11.79%), p-cymene (8.53%), camphene (7.01%), γ-terpinene (6.10%), α-pinene (4.55%) and caryophyllene (2.39%). The maximum inhibition efficiency (IE) (90%) was observed at the optimum concentration of 1.5 g/L. The electrochemical impedance spectroscopy data have shown that the formation of a protective film decrease the double layer capacitance and increases in the charge transfer resistance of mild steel. Increasing temperature reduces surface covered by the inhibitor, which results in a decrease of percentage inhibition efficiency from 89% to 76%. Polarization curves indicated that this EO can be classified as a mixed inhibitor in acidic medium with a predominant anodic inhibition. The value of enthalpy change is positive, which indicated endothermic adsorption process. The inhibition efficiencies calculated by weight loss exhibit a trend parallel to that of polarization and electrochemical impedance spectra measurements. We can conclude that essential oil extracted from T. Satureioides may be suggested as a green inhibitor against corrosion under acidic environment.

Keywords: Thymus satureioides, essential oil, mild steel, corrosion inhibition

Int. J. Corros. Scale Inhib., 2019, 8, no. 2, 291-305 PDF (696 K)
doi: 10.17675/2305-6894-2019-8-2-11

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