Rothmannia longiflora extract as corrosion inhibitor for mild steel in acidic media

The inhibitive effect of the aqueous extract of Rothmannia longiflora (RL) on the corrosion of mild steel in 1 M HCl and 0.5 M H 2 SO 4 solutions was investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The extract was found to efficiently inhibit the corrosion process in both environments and inhibition efficiency increased with increasing extract concentration as well as rise in temperature. Data from electrochemical measurements suggest that the extract functioned by adsorption of the organic matter on the metal/corrodent interface, inhibiting both the anodic and cathodic half reactions of the corrosion process. The result obtained from this study clearly shows that RL functioned as a good inhibitor for the corrosion of mild steel in 1 M HCl and 0.5 M H 2 SO 4 solutions and the inhibiting efficiency value increased with the inhibitor concentration. The adsorption of the RL on the mild steel surface in acid solution obeyed Langmuir adsorption isotherm.