CO2 Corrosion is a form of degradation that occurs when dissolved CO2 in condensate forms carbonic acid (H2CO3), which corrodes steels and low alloys to form an iron carbonate scale. CO2 corrosion is most typically found in boiler condensate return systems that are not adequately treated with corrosion inhibitors.
The rate of corrosion in materials affected by CO2 corrosion is dependant on several factors such as the concentration of CO2 in the environment, the operating conditions in which the components work, and the type of materials they are composed of. It’s also important to be aware of the water chemistry that is going on around the equipment; for example, alkaline water that has been de-aerated can build up incredibly high CO2 levels.
Water analysis is the best way to detect condensate problems that may lead to leaks in condensate return systems. Radiography or ultrasonic thickness measurements on the bottom of condensate piping and on the back side of elbows or other areas of higher velocity and/or turbulence may also detect localized thinning typical of condensate corrosion. To better avoid CO2 corrosion, one should adequately treat condensate return systems with corrosion inhibitors and upgrade various affected components to 304 SS.
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May/June 2005 Inspectioneering Journal
By John Reynolds at Intertek
Carbon dioxide (CO2) corrosion is most typically found in boiler condensate return systems that are not adequately treated with corrosion inhibitors (typically amines). Dissolved CO2 in condensate forms carbonic acid (H2CO3) which corrodes steels and low alloys to form a iron carbonate scale. |
