Eco-friendly Corrosion Inhibitors: Adsorption and Inhibitive Action of Ethanol Extracts of Chlomolaena Odorata L. for the Corrosion of Mild Steel in H2SO4 Solutions

The corrosion inhibition of mild steel in 0.5 M H2SO4 by ethanolic extract from the leaves of Chromolaena odorata L. (LECO) has been studied as a possible source of green inhibitor using the gravimetric technique in the temperature range 303-333 K. Results obtained showed that the LECO functioned as a corrosion inhibitor for mild steel in the acidic environment. Inhibition efficiency increased with extract concentration but decreased with temperature. At a concentration as low as 5 %v/v of the extract, the percentage inhibition reached about 95 % at 303 K and 89 % at 333 K. The thermodynamic parameters for the adsorption of this inhibitor on the metal surface such as Delta G(ads)degrees., were calculated using the Langmuir adsorption isotherm. The activation (E-a) energy and the heat of adsorption (Q(ads)) of the corrosion inhibition process suggest that the LECO molecules are physically adsorbed on the metal surface. The ethanolic Chlomolaena odorata L. leaves extract was found to be an excellent potential corrosion inhibitor because of the presence of essential oils, steroids, triterpenes, as well as the high content of a series of complex flavonoids, chalcones and flavones in the extract.