Under what condition does corrosion form in the flue pipe?

Corrosion in the flue pipe occurs when the flue gas temperature is below the dew point. When flue gas cools to a temperature below the dew point, moisture condenses within the flue pipe. This condensation creates a humid environment, which, when combined with the acidic components of the flue gas, particularly from burning fossil fuels, leads to the formation of corrosive substances. These substances can initiate and accelerate the corrosion process, damaging the integrity of the flue pipe over time.

Understanding the dew point is crucial in oil heating systems, as it indicates the temperature at which vapor turns into liquid. Maintaining temperatures above the dew point helps to avoid this condensation and the subsequent risks of corrosion. Other factors such as humidity and airflow can influence corrosion but are secondary to the critical relationship between flue gas temperature and dew point.