Corrosion of carbon steel in a buffered solution like NACE TM 0177 in the presence of hydrocarbon

Abstract

In this work, the study of the behavior of carbon steel AISI 1018 in a buffered solution of acetic acid and chlorides (electrolyte equivalent to the used in NACE TM 0177 method) with and without hydrocarbon is presented. The study took as starting point the results reported in literature about the corrosion mechanism in such system [1]. The electrochemical techniques used in this work were polarization curves and electrochemical impedance spectroscopy (EIS). The polarization curves obtained indicated that the anodic Tafel slopes do not suffer a significant change with the addition of hydrocarbon, while the cathodic ones suffered a slight change indicating the acceleration of the reduction reaction by the presence of the hydrocarbon. Electrochemical impedance spectroscopy shows that steel has a high activity in the solution studied which is most noticeable in low frequencies. This establishes that the interaction of acetic acid, acetate and chlorides with the metal is enhanced by the presence of hydrocarbon, where the adsorption processes are those that govern the corrosion mechanism. The adsorptions of corrosive agents prevent the formation and growth of a passive layer of corrosion products, even in the presence of hydrocarbon, so the corrosion rates obtained are high.