Acalypha wilkesiana acid extract as a potential green inhibitor for corrosion of mild steel in acidic medium: Thermodynamics and kinetics study

Abstract

The use of synthetic compounds as corrosion inhibitor is diminishing due to strict environmental regulations and toxic effects of the compounds on human beings and the environment. Consequently, there exists the need to develop a new class of corrosion inhibitors with low toxicity, eco-friendliness and good efficiency. Therefore, this study investigates the inhibitory potential of Acalypha wilkesiana (AWAE) extract on mild steel in 1M HCl using weight loss method. Experiments were performed by varying immersion period, concentration of the inhibitor and temperature. The results obtained showed a decrease in the corrosion rate of mild steel as the extract concentration increases while the inhibition efficiency increases with extract concentration. Effect of temperature on the inhibition efficiency showed an increase in inhibition efficiency with rise in temperature. The adsorption of the inhibitor on the mild steel surface in acid solution was found to obey the Langmuir adsorption isotherm. Calculated thermodynamic parameters revealed that the mechanism of the corrosion inhibition may be due to the chemical adsorption of the phyto-constituents on the surface of mild steel. Kinetic treatment of the data followed a first order reaction and the half-life values of the metal increase with increase in the extract concentration. Preliminary investigation of the phytochemical constituents showed that Acalypha wilkesiana contains tannin, flavonoid, saponin, alkaloid, steroid , terpenoid and some other compounds in trace quantity. FTIR results indicate that AWAE contains O and N atoms in functional groups and aromatic ring which meet the general consideration of a typical corrosion inhibitor.