Corrosion inhibition by Justicia gendarussa plant extract in hydrochloric acid solution

Corrosion inhibition effect of Justicia gendarussa extract (JGPE) on mild steel in 1 M HCl medium has been investigated by weight loss and electrochemical techniques. Inhibition efficiency of 93% was achieved with 150 ppm JGPE at 25 degrees C. The polarization studies showed that JGPE acts as mixed-type inhibitor. The Nyquist plots showed that on increasing JGPE concentration, increases charge transfer resistance and decreases double layer capacitance. JGPE obeys the Langmuir adsorption isotherm. AFM and ESCA confirmed the adsorption of JGPE on mild steel surface. Finally, JGPE inhibition efficiency was discussed in terms of adsorption and protective film formation. (C) 2009 Elsevier Ltd. All rights reserved.