Chemical Composition and Green Anticorrosive Potential of Thymus broussonnetii Boiss subsp. broussonnetii Essential Oils in Hydrochloric Acid Medium

The chemical composition of the essential oils of Thymus broussonnetii Boiss subsp. broussonnetii was carried out using GC/MS. The essential oils were characterized by carvacrol (39.51%) as the main constituent. The other components were benzene, 1-methyl-2-(1-methylethyl) (14.80%), gamma-terpinene (10.32%), alpha-pinene (9.7%), thymol (7.9%), and 3-cyclohexen-1-ol, 4-methyl-1-(1-methylethyl) (3.22%). The T. broussonnetii essential oils were tested for their potential to inhibit the corrosion of C38 steel in acidic environment. The effect of inhibition was studied using weight loss measurements and electrochemical techniques [potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS)] in the presence of different concentrations of T. broussonnetii essential oils ranging from 0.05 to 2 g/L. We obtained 82.35% of the inhibition efficiency at 2 g/L of the essential oils using the EIS test. The polarization studies showed that T. broussonnetii essential oils inhibit both cathodic hydrogen reduction reactions and anodic metal dissolution, and they act as mixed-type inhibitors of corrosion. The inhibition efficiency increases with increasing the temperature. The highest inhibition efficiency was 90% reached at 328 K. Adsorption of T. broussonnetii essential oils on the surface of the steel follows the isotherm of Langmuir. T. broussonnetii essential oils are a natural and environmentally eco-friendly inhibitor; they can be used as an alternative to toxic chemical inhibitors especially in acidic medium.