Mitigating CO2 Corrosion of Natural Gas Steel Pipelines by Thermal Spray Aluminum Coatings

Internal pipeline corrosion due to carbon dioxide (CO2) is a major challenge facing the oil and gas industry. The objective of this study was to investigate the corrosion behavior of aluminum (Al)-based alloys as sacrificial coatings to protect pipelines in a CO2-saturated aqueous electrolyte (3.5 wt% NaCl) at 4 bar CO2 partial pressure (3 bar) and 40°C. The corrosion resistance of Al-based alloys and thermal spray coatings was evaluated in an electrochemical reaction autoclave using electrochemical methods (potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy). Post-corrosion surface characterization was performed by scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy. The obtained data show Al-based alloys demonstrated promising protection against CO2 corrosion with no breakaway degradation issues.