2205 Duplex
PREN ~34-36
Standard offshore
Cost-effective
Max seawater: ~25°C
2507 Super Duplex
PREN ~42-44
Warm seawater OK
Subsea standard
Higher strength
Chemical Composition
| Property | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| PREN | 34-36 | 42-44 |
| Chromium (Cr) | 22-23% | 24-26% |
| Molybdenum (Mo) | 3-3.5% | 3-4% |
| Nickel (Ni) | 4.5-6.5% | 6-8% |
| Nitrogen (N) | 0.14-0.20% | 0.24-0.32% |
| UNS Number | S31803 / S32205 | S32750 |
| EN Number | 1.4462 | 1.4410 |
When to Use 2205 vs 2507
Choose Duplex 2205 when:
- Chloride environment below 25°C (e.g., temperate coastal waters)
- General chemical processing, tanks, pressure vessels
- Architecture and building facades
- Paper and pulp processing equipment
- Budget-conscious projects where 316L won't work but 2507 is overkill
Choose Super Duplex 2507 when:
- Seawater service above 30°C or tropical offshore conditions
- Offshore wind subsea hardware (J-tube clamps, cable cleats, sea chests)
- Desalination plant brine passages
- Oil and gas topside process vessels with high chloride
- Any application where 2205 has shown pitting or crevice corrosion
⚠️ Offshore Wind Specification Change
Most major offshore wind developers (Vestas, Siemens Gamesa) have updated their specifications to require Super Duplex 2507 for all subsea seawater-exposed components. This includes J-tube interface clamps, cable supports, and internal structural brackets in the splash zone. Duplex 2205 is no longer accepted for these applications in new projects. Always check the project-specific material specification before ordering.
Mechanical Properties
| Property | Duplex 2205 | Super Duplex 2507 |
|---|---|---|
| Yield Strength (MPa) | 450 (min) | 550 (min) |
| Tensile Strength (MPa) | 655 (min) | 800 (min) |
| Elongation (%) | 25 (min) | 15 (min) |
| Hardness (HB) | ≤293 | ≤310 |
| PREN (typical) | 35 | 43 |
Welding
Both 2205 and 2507 are welded with matching duplex filler wire (AWS A5.4 E2209 / ER2209). Critical requirements:
- Interpass temperature: 2205 ≤ 150°C; 2507 ≤ 100°C (stricter for 2507)
- Root pass protection: argon purge required to prevent oxidation
- Never PWHT: post-weld heat treatment causes sigma phase embrittlement
- Heat input: moderate (0.5-1.5 kJ/mm) — too low risks lack of fusion, too high risks sigma phase
Need Duplex or Super Duplex Materials?
Send your requirements — grade, form, dimensions, ASTM spec, and quantity. Mill certificates and third-party inspection available.
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