API 571 Certification (Corrosion & Materials) Practice Test

Which family of alloys shows improved resistance to fuel ash corrosion?

1. Alloy 400

2. 50Cr-50Ni family

3. 300 series stainless

4. Low Alloy Steel

The correct answer is: 50Cr-50Ni family

The 50Cr-50Ni family of alloys is known for its excellent resistance to fuel ash corrosion due to its high chromium and nickel content. The presence of chromium enhances the formation of a protective oxide layer on the surface of the alloy, which significantly contributes to its resistance against corrosive environments, particularly those involving high-temperature exposure to fuel ash. Nickel also plays a critical role in improving the overall mechanical properties and resistance to thermal cycling, which are factors relevant in environments where fuel ash is present. This combination of elements results in a material that can withstand the corrosive effects associated with combustion processes, making this family of alloys particularly suitable for applications such as gas turbines and other areas where fuel ash corrosion can be a concern. In contrast, other alloy families mentioned may not provide the same level of protection. The other alloy types, while they have their specific applications, do not possess the same balance of elements that is critical for resisting fuel ash corrosion.