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

Abstract

Internal pipeline corrosion due to CO2 is a major challenge facing the oil and gas industry. To protect the pipelines and equipment from the ravages of CO2 corrosion, novel sacrificial coatings can be used. The objective of this study was to investigate the corrosion behavior of 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 barg) and 40 oC. 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.

Carbon Dioxide Corrosion Mechanisms: Historical Development and Key Parameters of CO2-H2O Systems

“…Metallic coatings have a similar effect to cathodic protection, where a more reactive metal (nickel, zinc, chromium, tin, aluminum, copper, and others) is applied on the steel surface and acts as a sacrificial layer to protect against corrosion. A recent study by Belarbi et al [123] reported the use of thermal spray aluminum (TSA) coatings to protect gas pipelines from internal CO 2 corrosion. The TSA coating protected the carbon steel surface, and no localized corrosion was observed at 40 °C and 4 bar of CO 2 .…”