Impact of Internal CO2 Corrosion of Mild Steel Pipelines on Solid Hydrate Particles

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Product Number: 51321-16391-SG

Author: Zachary Aman/Bruce Norris/Mariano Iannuzzi/Eric May

Publication Date: 2021

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This work focuses on the interplay between protective iron carbonate surface scales and hydrate particles deposition. An iron carbonate layer was formed on API 5L X65 carbon steel in a glass reactor cell under aqueous CO2 saturated conditions using a three-electrode system. The protectiveness of the surface film was determined in situ using electrochemical techniques, which included open-circuit potential (OCP) and linear polarization (LP) measurements. As expected, the microscopic surface layer acted as a mass-transfer barrier, which reduced the corrosion rate of the carbon steel sample to various degrees depending on the pH of the electrolyte and polarization condition. After testing, the structure and composition of the films were characterized using surface analysis techniques, including, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The influence of the surface film on hydrate adhesion was subsequently investigated using a micromechanical force (MMF) apparatus, which indirectly measures the adhesion force between a clathrate hydrate particle and a nominated solid substrate surface. The combination of methods enabled the comparison of how corrosion products and surface film formation affect hydrate deposition tendency. Results indicate that the presence of an iron carbonate layer increases the propensity for hydrate deposition, through both higher growth rates.

Key words: Hydrates, Corrosion, Carbon Steel, Carbon Dioxide, Electrochemistry, Scale