Localized CO₂ Corrosion due to Galvanic Effect on the Surface of API 5L X65 Steel in the Presence of Iron Carbonate Corrosion Product

Localized CO₂ corrosion is one of the most significant concerns for mild steels used in the oil and gas industry. The formation of iron carbonate on the steel surface under CO₂ corrosion conditions can lead to localized corrosion. The degradation of this corrosion product in specific areas, influenced by factors such as fluid velocity, creates a galvanic couple between the protected and unprotected steel surfaces. This study employs the artificial pit method and zero-resistance ammetery technique to investigate this galvanic couple. The effects of temperature, pH, inhibitor, and NaCl salt concentration on the galvanic current density between iron carbonate-covered and bare areas of API 5L X65 carbon steel were examined. Results indicate that high salt concentration, low pH, and lower temperatures increase the galvanic current density between the FeCO₃-covered and bare areas.