Origanum Elongatum as a Green Corrosion Inhibitor for C38 Steel in an Acidic Medium

Abstract

The extract of Origanum elongatum Emb. and Maire (OEE) was used as a corrosion inhibitor for C38 steel in 1N HCl medium, the inhibitory effect was studied by different techniques, weight loss and electrochemical measurements. Weight loss measurements indicate a maximum efficiency of 77.50% at a concentration of 1 g/L at 298 K. The potentiodynamic polarization shows that OEE is a mixed type of inhibitor. Electrical impedance spectroscopy measurements show an increase in charge transfer resistance accompanied by a decrease in double layer capacitance, suggesting that the OEE extract acts by adsorption on the metal surface, the decrease in the double layer is always related to the decrease in the dielectric constant and/or the increase in the thickness of the electrical double layer. Adsorption of active OEE species in 1N HCl on C38 steel follows Langmuir isotherm. A fractionation was performed on the OEE, which resulted in three different fractions. These fractions and the OEE were analysed by infrared spectroscopy, the inhibitory efficiencies of the fractions were tested by the weight loss measurements.