Anticorrosion properties of Thymus munbyanus Boiss & Reut

  The analysis of essential oil of Thymus munbyanus Boiss & Reut (TM oil) by GC and led to the identification of 32 components accounting for (97.8%) of the total oils were identified. The main compounds of essential oils of Thymus munbyanus were carvacrol (31.7%), g-terpinene (21.9%), p-cymene (14.7%), thymol (7.6%), linalool (4.3%), borneol (3.9%) and α-terpinene (2.1%). The inhibitive effect of TM oil on the corrosion of mild steel in 1M HCl solution has been investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The corrosion rate calculated by polarization potentiodynamic curves obtained after 30min from immersion in 1M HCl medium. The gravimetric results indicate that TM oil exhibited good inhibition efficiency in 1M HCl solution. The polarization measurements showed that the studied inhibitor is a mixed type with a significant reduction of cathodic and anodic current densities. Electrochemical impedance spectroscopy measurements revealed that the charge transfer resistance increased by increasing the essential oil concentration, which suggests Langmuir isotherm model as a most suitable adsorption mechanism.