Inhibition of Steel Corrosion in 1 M HCl by the Essential Oil of Thymus pallidus

The composition of the essential oil isolated from the aerial parts of Thymus pallidus an endemic plant from Morocco was investigated by GC and GC/MS. The oil of T. pallidus was found to be rich in monoterpenes hydrocarbons, with borneol (36.6%) being the major component. The effect of Thymus pallidus essential oil extract as a corrosion inhibitor on the corrosion rate of Carbon Steel (CS) in hydrochlorid acid environment was investigated using gravimetric method potentiodynamic polarizations and electrochemical impedance spectroscopy (EIS) methods. The corrosion rates were studied in different concentrations of T. pallidus oil at 298 K. The results revealed that T. pallidus oil in acid environment decreased the corrosion rate at various concentrations considered. The maximum inhibition efficiency of 88.65 % was achieved with 1.0 g/l inhibitor concentration at 298K. Polarization measurements show also that T. pallidus oil act as good mixed inhibitor. The results demonstrated that T. pallidus oil adsorbed on the surface of carbon steel and obeyed Langmuir adsorption isotherm.