Corrosion Inhibition of Steel in 1 M Hydrochloric Acid Medium by Thymus leptobotrys Essential Oils

Abstract

The aim of this study is the evaluation of the inhibitory potential of Thymus leptobotrys essential oils on corrosion of carbon steel in 1 M HCl.  The essential oils obtained by hydro-distillation using Clevenger were analyzed by gas phase chromatography coupled to a mass spectrum (GC/MS). Carvacrol (63.38%) was the main compound of T. leptobotrys essential oil, followed of p-cymene(8.34%), borneol (5.85%), linalool (3.12%), camphene (2.70%), α-pinene (2.69%) and the sesquiterpene hydrocarbon β-caryophyllene (2.46%). The inhibitive action of Thymus leptobotrys essential oils was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and effect of temperature. The inhibition efficiency was found to increasewith oil content to attain 86.95% at 2 g/L. The measurements show that inhibition efficiencies increase with the increasing of T. leptobotrys concentrations but decrease with increasing temperature. The results showed that T. leptobotrys acted as a mixed-type corrosion inhibitor. This was supported by the impedance measurements which showed a change in the charge transfer resistance and double layer capacitance, indicating the adsorption of T. leptobotrys on the carbon steel surface. Thermodynamic parameters of the studied inhibitor were calculated and discussed.