Study of the Top-of-the-Line Corrosion Using a Novel Electrochemical Probe

Abstract

Top-of-the-line corrosion (TLC) is a concern for subsea wet-gas transportation pipelines operating in a stratified flow regime. The insufficient volume of electrolyte at the top of the line combined with the low electrical conductivity of the condensed liquid has confined the majority of TLC studies to the weight loss method which only provides integrated corrosion rate over long period of exposure. The instantaneous monitoring of TLC rates using electrochemical methods is still a challenge for researchers and in the field. To overcome this limitation, this study presents a novel TLC monitoring cell capable of measuring in situ corrosion rates of carbon steel under condensing condition by electrochemical methods such as linear polarization resistance, electrochemical impedance spectroscopy, and electrochemical frequency modulation. The data presented in this paper have been conducted over 5 d at varying condensation rates to evaluate the feasibility and accuracy of the methods applied. In addition, TLC rates have also been measured by weight loss and monitored in situ by measuring the iron concentration in the condensed liquids in order to compare these results with electrochemical methods. Both the electrochemical and non-electrochemical methods provide comparable results, which validates the design and efficacy of the probe. Therefore, the probe appears to be a promising tool for further investigation into the TLC process and its inhibition.