Duplex 2205 vs. Super Duplex 2507: High-Strength Corrosion Resistance Explained
1. What is “Duplex”? Duplex stainless steels have a two-phase microstructure consisting of grains of both Austenitic and Ferritic stainless steel (roughly 50/50). This unique combination provides the best of both worlds: the corrosion resistance of 300-series stainless and the high yield strength of ferritic steel.
2. Key Grades
- Duplex 2205 (UNS S31803/S32205): The workhorse grade. Offers twice the strength of SS316 and superior resistance to Stress Corrosion Cracking (SCC).
- Super Duplex 2507 (UNS S32750): Features higher Chromium, Molybdenum, and Nitrogen levels, designed for extremely aggressive environments like seawater.
3. The PREN Value The Pitting Resistance Equivalent Number (PREN) for 2205 is typically >34, while 2507 is >40. For comparison, standard SS316 is only around 24.
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