Corrosion of Carbon Steel in CO2-Saturated Brines Investigated By Rotating Disk Electrode and Scanning Vibrating Electrode Technique

Abstract

CO2 corrosion has been extensively studied because dissolved CO2 makes carbon steels susceptible to corrosion and failure during oil and natural gas exploration, production, transmission, and processing as well as in CO2 sequestration and capture systems. A rotating disk electrode (RDE) system and the scanning vibrating electrode technique (SVET) were used to study CO2 corrosion, including localized corrosion that often occurs when dissolved CO2 is present, especially at higher pH. The carbon steel, which meets the American Petroleum Institute 5L grade X65 standard, was investigated in 3.5%wt NaCl solutions from pH 4 to 8 at 30 oC. The effects of CO2, pH, and mass transport were studied. In situ electrochemical measurements were carried out in the RDE system at different rotating rates to measure the corrosion rates and determine the corrosion mechanism, including linear polarization resistance, electrochemical impedance spectroscopy, electrochemical frequency modulation, cyclic voltammetry, and Tafel analysis. Surface analysis using scanning electron microscopy and X-ray photoelectron spectroscopy was performed on the corroded samples. SVET was used to characterize the localized corrosion on the steel surfaces at different conditions.