Boerhavia diffusa (Punarnava) Root Extract as Green Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution: Theoretical and Electrochemical studies

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 -E-corr 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 (R-ct) value of inhibited system increased from 68 Omega cm(2) to 426 Omega cm(2) and double layer capacitance (C-dl) value decreased from 37 mu Fcm(-2) to 17 mu Fcm(-2) with increasing inhibitor concentration. Langmuir adsorption isotherm was followed by the inhibitor molecules on steel surface. The low value of energy gap (Delta E) further provided support for high efficiency of the extract.