No abstract

Synthetic compounds certainly exhibit good anticorrosive activity but also toxicity for humans and their environment. Because of these concerns, we turned to more environmentally friendly substances such as essential oils and of course other types of plant extracts. These products are considered green corrosion inhibitors. In this present study, we propose to make a comparative study of the inhibitory effect of extracts of two different essential oils, Eucalyptus camaldulensis (EC) and Cyperus rotundus (CR) on the corrosion of structural steel S235 in the medium 1 M hydrochloric acid. This inhibitory action was studied using potentiodynamic polarization measurements and electrochemical impedance spectroscopy. The GC-MS analysis of the essential oils extracts showed that EC contains 96.2% oxygenated terpenes (90.6% monoterpenes and 5.6% sesquiterpenes), whereas CR includes 78.1% oxygenated terpenes (70.6% sesquiterpenes and 7.5% monoterpenes). Polarization measurements indicate that EC and CR are mixed inhibitors. The experimental results gave an inhibition efficiency close to 78.9% for EC and 86.7% for CR for an inhibitor concentration of 4 gL -1 at 293 K. The inhibition performances of these essential oils were correlated with their composition. The adsorption of the molecules of the oils responsible for the inhibition on the surface of the steel, in the hydrochloric acid solution, obeys the Langmuir adsorption isotherm. This present work has therefore shown that these two types of essential oils have a good inhibitory effectiveness on the corrosion of the metal S235 in 1M hydrochloric acid solution.