API 571 Certification (Corrosion & Materials) Practice Test

Which series of stainless steels is least susceptible to metal dusting?

1. 400 series stainless

2. 300 series stainless

3. Nickel based alloys

4. Low Alloy Steel

The correct answer is: 300 series stainless

The 300 series stainless steels, which are austenitic stainless steels, have a notably low susceptibility to metal dusting due to their high nickel and chromium content. These elements enhance the corrosion resistance and stability of the steel at elevated temperatures, which is a critical factor in environments that foster metal dusting. Metal dusting is a form of corrosion that occurs in high-temperature environments, particularly in the presence of carbon, where carbon can react with the metal to form fine metal particles, producing a dust-like appearance. The austenitic structure of the 300 series stainless steels provides a more stable matrix that resists the adverse effects of this reaction compared to other stainless steel types. In contrast, the other materials listed tend to have different compositions or microstructures that do not offer the same level of protection against metal dusting. For example, the 400 series stainless steels are martensitic and generally have lower nickel content, making them less resistant to such corrosive conditions. Nickel-based alloys do have good resistance to various forms of corrosion, but their behavior in metal dusting-specific environments may vary based on the specific alloy and conditions. Low alloy steels are also more susceptible because of their lower chromium and nickel content, which do not provide the same resistance.