CO2 Top-of-Line-Corrosion; Assessing the Role of Acetic Acid on General and Pitting Corrosion

Four different water condensation rates/temperature top-of-line corrosion (TLC) conditions were selected to study the role of acetic acid (HAc) on both the kinetics and mechanism of carbon steel dissolution. A miniature three-electrode setup was developed to characterize the real-time TLC response through the implementation of electrochemical measurements. Surface analysis techniques (microscopy and profilometry) were also conducted to complement the electrochemical results. Collective consideration of the corrosion response and condensate chemistry indicated that similar effects were observed to those reported in the literature for bulk aqueous environments, in that the introduction of HAc could result in either accentuation or a minimal/inhibitive effect on general corrosion depending upon the operating conditions. The minimal/inhibitive effects of HAc were apparent at a surface temperature of 20.5°C and water condensation rate of 0.5 mL/m2·s, as no significant increase in corrosion was observed, despite a significant reduction in condensate pH being generated by the presence of HAc. X-ray photoelectron spectroscopy analysis of the inhibited steel specimen in the presence of HAc revealed the presence of iron acetate on the steel surface, which may have been at least partially responsible for the observed inhibitive effect. Extended duration experiments over 96 hr revealed that both general and localized corrosion are not significantly affected by HAc addition at low temperature, while the level of degradation increased at higher surface temperature over longer periods.