Duplex 2205 vs Super Duplex 2507
When 2205 reaches its chloride limit, 2507 takes over. The premium is modest (50-70% over 2205) for a quantum leap in hot seawater and sour service performance.
| Property | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| UNS | S32205 | S32750 |
| Chromium | 21.0 – 23.0% | 24.0 – 26.0% |
| Molybdenum | 2.5 – 3.5% | 3.0 – 5.0% |
| Nickel | 4.5 – 6.5% | 6.0 – 8.0% |
| Nitrogen | 0.08 – 0.20% | 0.24 – 0.32% |
| Tensile Strength | ≥ 655 MPa | ≥ 800 MPa |
| Yield Strength | ≥ 450 MPa | ≥ 550 MPa |
| PREN | 34 – 38 | 40 – 43 |
| Critical Pitting Temp | 40 – 50°C | 70 – 85°C |
| NACE Hardness Limit | ≤ 28 HRC | ≤ 32 HRC |
| Relative Cost | 1.0× (base) | 1.5 – 1.7× |
Choose 2205 When:
- Seawater cooling below 40°C
- General offshore process piping (sweet or mildly sour)
- Desalination pre-treatment and permeate lines
- Budget-sensitive projects
Choose 2507 When:
- Hot seawater above 40°C (MED/MSF, geothermal)
- Deepwater subsea (zero maintenance access)
- Aggressive sour service (H₂S + high Cl⁻)
- Brine concentrators and chemical injection
The Bottom Line
2205 handles 90% of offshore and desalination applications. Upgrade to 2507 when: (1) seawater temperature exceeds 40°C continuously; (2) deepwater subsea where a single intervention costs $1M+; (3) PREN requirement exceeds 40. For most topsides and shallow-water applications, 2205 is the cost-optimal duplex choice.