Corrosion inhibition of Mild Steel at Elevated temperature in highly Acidic Brines using a green corrosion inhibitor

Abstract

Corrosion Inhibition of mild steel in 5 M Hydrochloric acid solution at different temperatures was investigated using a new green corrosion inhibitor (lauramidopropylamine oxide). Various electrochemical techniques and surface characterization techniques including, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM), were utilized in this study. The kinetics of corrosion and thermodynamic parameters were calculated and discussed. The results have shown that corrosion rate of mild steel was significantly reduced with a maximum inhibition efficiency of more than 94% at a concentration of 370 µmol L-1 of the inhibitor. The adsorption of lauramidopropylamine oxide corrosion inhibitor on the metallic substrate obeys Langmuir's adsorption isotherm. Examination of polarization curves indicated that the inhibitor is of a mixed type since it inhibits both anodic as well as cathodic reaction. Additionally, the adsorption of the inhibitor on the surface was found to be chemi-physisorption. Analyses of surface topography of the mild steel revealed an appreciable decrease in the surface roughness when the inhibitor was used compared to the uninhibited acidic solution. The energy dispersive x-ray (EDX) and x-ray photoelectron spectroscopy (XPS) revealed the presence of nitrogen on the mild steel, which confirmed the adsorption of the corrosion inhibitor molecules on the surface. This work provides a promising eco solution for mitigating corrosion of mild steel in an aggressive acidic environment. It will also contribute to a significant cost saving, not only in Qatar but worldwide too.