Electrochemical Noise Study on Corrosion of Low Carbon Pipeline Steel in Sour Solutions

Abstract

Electrochemical Noise (EN) measurements for low carbon pipeline steel (X52) samples were carried out in 3.5% NaCl aqueous and NACE solutions. Both testing solutions were saturated with hydrogen sulphide (H2S) at 20 and 60 oC, under static conditions. EN data was analysed in the time domain. Parameter such as Electrochemical Noise Resistance (Rn) and Localization Index (LI) were determined from the analysis in the time domain. Also, Rn results are compared with traditional Linear Polarization Resistance (LPR) data. A superficial analysis was carried out by a scanning electron microscopy (SEM) with Energy Dispersive X-Ray analyses (EDX). A good correlation was observed among the used techniques and relevant electrochemical data related to the corrosion phenomena was obtained. According to Rn, the corrosion rate (CR) values of the steel sample immersed in 3.5% NaCl are higher than the CR of the steel samples immersed in NACE solution. The morphology of the corrosion process obtained by SEM was a localized type and this behaviour was corroborated by the results obtained by LI where these LI values are 1 or close to 1.