Chemical composition, adsorption proprieties and corrosion inhibition on mild steel of Mentha rotundifolia L. essential oil from Morocco

The analysis of Mentha rotundifolia L. essential oil by Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (GC/MS) allowed the identification of 25 components, which accounted for 94.3% of the total oil. Pulegone (69.1%) and menthone (18.5%) were identified as main compounds. The inhibitive effect of this essential 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 gravimetric results indicate that MR oil exhibits good inhibition efficiency in 1M HCl solution. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 303–333K. Polarization measurements showed that the studied inhibitor is mixed type with significant reduction of cathodic and anodic current densities. Electrochemical impedance spectroscopy measurements revealed that the charge transfer resistance increases with increase in the concentration of essential oil. Various activation parameters such as activation energy, activation enthalpy and activation entropy are evaluated and discussed. Adsorption thermodynamic parameters are also computed. Linearity of Langmuir isotherm adsorptions indicated the monolayer formation of inhibitor on mild steel surface.