Abstract
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 H2SO4 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 H2SO4 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.
Highlights
Background 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 H2SO4 solutions was investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy measurements
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 H2SO4 solutions and the inhibiting efficiency value increased with the inhibitor concentration
The extract can be seen to exhibit corrosion inhibiting effects in both acid media, at all concentration used in this study, reaching a maximum inhibition efficiency (IE) of 90.92 and 96.50 % in 1.0 M HCl and 0.5 M H2SO4 solutions at the optimum concentration of 1000 mg/L
Summary
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 H2SO4 solutions was investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Several researchers [1,2,3,4,5,6,7,8,9] have studied the effects of some synthetic organic inhibitors on the corrosion of steel in hydrochloric and sulphuric acid solutions The efficiency of these inhibitors is related to the presence of polar functions with S, O or N atoms in the molecule, heterocyclic compounds and p-electrons [10,11,12]. The known hazardous effects of most synthetic organic inhibitors and restrictive environmental regulations [15] have made it necessary to search for cheaper, non-toxic and environmentally friendly natural products as corrosion inhibitors These natural organic compounds are either synthesized or extracted from aromatic herbs, spices and medicinal plants. The results from these studies confirm that biomass extracts possess remarkable abilities to inhibit the corrosion reaction
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