API 571 Certification (Corrosion & Materials) Practice Test

What type of corrosion is flue gas dew point corrosion associated with?

1. Carbon steels

2. High-strength nickel alloys

3. Aluminum alloys

4. Copper alloys

The correct answer is: Carbon steels

Flue gas dew point corrosion is primarily associated with carbon steels due to the conditions that promote its occurrence. This type of corrosion happens when the temperature of flue gases falls below their dew point, causing condensation of water vapor in the presence of acidic components, particularly sulfuric acid or hydrochloric acid from the combustion of fossil fuels. Carbon steels are more susceptible to this type of corrosion because they have a relatively high susceptibility to the acidic environments that result from the condensation process. When the acidic condensate forms on the steel surfaces, it can lead to localized pitting and general corrosion, significantly weakening the material. In contrast, high-strength nickel alloys, aluminum alloys, and copper alloys generally possess better corrosion resistance in acidic environments compared to carbon steels. Nickel alloys, for instance, are often designed to withstand harsh chemical conditions, while aluminum alloys often form a protective oxide layer that can help prevent corrosion. Copper alloys also have inherent properties that provide better resistance to corrosion mechanisms than carbon steels, making them less likely to be affected by flue gas dew point corrosion. Thus, the association of flue gas dew point corrosion with carbon steels highlights their vulnerability under specific environmental conditions.