Electrochemical study of carbon steel corrosion in buffered acetic acid solutions with chlorides and H2S

In this work, the corrosion behavior of SAE 1018 carbon steel in buffered acetic acid (HAc) solutions containing chlorides, with and without H2S, was studied. Polarization curves obtained by different electrochemical techniques, indicate negligible modification of anodic slopes when adding H2S; however, the cathodic branch is more sensitive showing an accelerated reduction reaction in the presence of H2S. Interface characterization was performed by electrochemical impedance technique (EIS) in the absence and presence of H2S and near to the corrosion potential (E-corr). Analysis of results shows no film of corrosion products, since the impedance spectra characteristics indicate a great activity of steel in the solutions studied, with differences only at low frequencies. The adsorbed complexes formed in the solution containing HAc, acetate and chlorides control the corrosion process and prevent passive film formation, even in the presence of H2S. (C) 2002 Elsevier Science Ltd. All rights reserved.