Which material has the highest resistance to sulfidation?

Which material has the highest resistance to sulfidation?

• A. Carbon steel
• B. Stainless steel 316
• C. Titanium
• D. 18/8 stainless steel

Answer: (D)

Sulfidation resistance depends on how well a material can form and maintain a protective surface film that slows sulfur diffusion into the metal. Carbon steel offers little protection because it lacks alloying elements that form a stable protective scale, so iron sulfide tends to develop quickly and grow, leading to rapid degradation. Titanium does form a very strong oxide layer, but in sulfidizing environments at high temperature sulfur compounds can still interact with titanium and compromise the protective film, narrowing its advantage in these specific conditions. Among the stainless steels listed, the 18/8 grade (304) has a balance of chromium and nickel that supports a durable, adherent chromium oxide layer, which is particularly effective at resisting sulfur attack in typical sulfidation scenarios. The combination of a stable oxide film and slower sulfur diffusion makes it more resistant in these environments than the other options, including stainless 316 and carbon steel, so it ranks highest for sulfidation resistance in this context.

Sulfidation resistance depends on how well a material can form and maintain a protective surface film that slows sulfur diffusion into the metal. Carbon steel offers little protection because it lacks alloying elements that form a stable protective scale, so iron sulfide tends to develop quickly and grow, leading to rapid degradation. Titanium does form a very strong oxide layer, but in sulfidizing environments at high temperature sulfur compounds can still interact with titanium and compromise the protective film, narrowing its advantage in these specific conditions. Among the stainless steels listed, the 18/8 grade (304) has a balance of chromium and nickel that supports a durable, adherent chromium oxide layer, which is particularly effective at resisting sulfur attack in typical sulfidation scenarios. The combination of a stable oxide film and slower sulfur diffusion makes it more resistant in these environments than the other options, including stainless 316 and carbon steel, so it ranks highest for sulfidation resistance in this context.