API 571 Certification (Corrosion & Materials) Practice Test

What type of material commonly experiences hot corrosion at elevated temperatures?

1. High Silicon Cast Iron

2. Nickel alloys

3. Carbon steels

4. Alloy B-2

The correct answer is: Nickel alloys

Hot corrosion is a specific type of corrosion that typically occurs at elevated temperatures, often in environments that contain aggressive agents like salts and sulfates. Nickel alloys are particularly known to experience hot corrosion due to their high-performance applications, especially in gas turbines, industrial engines, and other high-temperature environments. The composition of nickel alloys often includes elements like chromium, which provide some resistance to corrosion, but these materials can still succumb to hot corrosion when subjected to conditions that include high temperatures and the presence of corrosive substances. The mechanism of hot corrosion is often accelerated by the formation of a molten salt layer at high temperatures, which can lead to rapid degradation of the material. Materials such as high silicon cast iron, carbon steels, and Alloy B-2 do not typically face the same level of risk under these conditions. High silicon cast iron may have some resistance due to silicon enhancing oxidation resistance, but it is not used in the same high-temperature applications where hot corrosion is a significant concern. Carbon steels are generally not suitable for elevated temperature applications where hot corrosion would be a risk. Alloy B-2, primarily a nickel-molybdenum alloy, has good corrosion resistance, but it's specifically designed for different types of corrosion rather than hot corrosion at high temperatures.