The influence of oxygen on the morphology and protectiveness of iron carbonate scales formed on carbon steel in CO2 environments at near-neutral pH was investigated. Specimens were tensioned in four-point bending jigs for stress corrosion cracking tests, and unloaded specimens were used for electrochemical tests. All specimens were exposed to CO2 aqueous solutions with and without dissolved oxygen, and corrosion rates were monitored by linear polarization resistance technique. Corrosion scales were characterized by scanning electron microscopy and X-ray diffraction, while the analysis of the corroded surface of the specimens after scale removal was carried out using scanning electron microscopy and optical profilometry. The iron carbonate scales were destabilized and became less protective in the presence of oxygen, which resulted in localized attacks, but no cracks were observed.

Subject
Scanning electron microscopy, Water, Corrosion rate, Annulus, Siderite, Corrosion products, Corrosion scales, Surface analysis, Iron carbonate scale, Scale formation, Dissolved oxygen, Corrosion protection, Linear polarization resistance
Keywords:
carbon dioxide, carbon steel, corrosion, flexible pipes, iron carbonate, iron oxy-hydroxide, near-neutral pH, oxygen, stress corrosion cracking
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2022
Association for Materials Protection and Performance (AMPP)
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