Boerhavia diffusa (punarnava) root extract as green corrosion inhibitor for mild steel in hydrochloric acid solution: Theoretical and electrochemical studies

Abstract

The effect of extract of Punarnava (Boerhavia diffusa) on corrosion of mild steel was investigated by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy. Tafel polarization results revealed that the maximum displacement of -Ecorr value is 46 mV hence the extract acted as mixed-type inhibitor. The inhibition efficiency increases up to 96% at 300 ppm and decreases with increase in the temperature. The charge transfer resistance (Rct) value of inhibited system increased from 68 Ω cm2 to 426 Ω cm2 and double layer capacitance (Cdl) value decreased from 37 μFcm-2 to 17μFcm-2 with increasing inhibitor concentration. Langmuir adsorption isotherm was followed by the inhibitor molecules on steel surface. The low value of energy gap (δE) further provided support for high efficiency of the extract. © 2012 by ESG.