Studies onRhoeo discolorplant extract as a natural corrosion inhibitor

Abstract

The use of plant extracts as natural corrosion inhibitors is gaining prominence as they contain different organic compounds adsorbed on the surface of metals. Studies were carried out on the ethanolic extract of the abundantly available Rhoeo discolor leaves, commonly known as boat lily, as it is a natural inhibitor in hydrochloric acid (HCl) (0.1–0.5 M) on mild steel. R. discolor plant extract is biodegradable, cheap and readily available in nature. Inhibition efficiencies were obtained from weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopic study at 30°C. A scanning electron microscopy report confirms the adsorption of the inhibitor on mild steel. Fourier transform infrared spectroscopy and gas chromatography and mass spectroscopy reports support the presence of functional groups in the inhibitor. The effect of inhibitor dosage from 0.1 to 0.5 g/l is investigated at 30°C. Corrosion inhibition efficiency for mild steel in 0.1 M of hydrochloric acid and 0.5 g/l of inhibitor is found to be maximum at 94.6% estimated by the weight loss method. The potentiodynamic polarisation method indicates 85.28%, and it stands at 88.60% by the impedance method. Results suggest that R. discolor acts as a good inhibitor of the corrosion process on mild steel.