Investigation of Salvadora persica Roots Extract as Corrosion Inhibitor for Mild Steel in 1 M HCl and in Cooling Water

Abstract

Plant extracts have become important as an environmentally acceptable, readily available and renewable source for wide range of inhibitors. Therefore, inhibition of the corrosion of mild steel in hydrochloric acid solution and cooling water was carryout by the root extract of Miswak (Salvadora persica) has been studied using weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Inhibition was found to increase with increasing concentration of the extract. The effect of immersion time on the corrosion behavior of mild steel in 1 M HCl and cooling water with addition of extract was also studied. The adsorption of the extract on the mild steel surface obeyed the Langmuir adsorption isotherm. Values of inhibition efficiency calculated from weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) are in good agreement. Polarization curves showed that root extract behaves as a mixed-type inhibitor in both hydrochloric acid and cooling water. The adsorbed film on mild steel surface containing extract was also measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results obtained showed that the root extract could serve as effective inhibitor of the corrosion of mild steel in both hydrochloric acid media and cooling water media.

Keywords: Miswak, Corrosion inhibitor, Cooling water, SEM and AFM.