Duplex 2205 is a stainless steel with a mixed austenite-ferrite structure. It is about twice as strong as 304 or 316 and resists chloride pitting and stress corrosion cracking much better. It is used in chemical plants, oil and gas, desalination and seawater equipment.
Quick facts
- Type
- Duplex (austenitic-ferritic) stainless steel
- Main alloys
- About 22% chromium, 5% nickel, 3% molybdenum, nitrogen
- Yield strength
- About 450 MPa or more (roughly twice 316)
- Corrosion (PREN)
- About 34–36, better than 316 (about 24)
- Magnetic
- Yes, partly (ferrite)
- Temperature
- Generally used below about 280–300 °C
Equivalent grades
| Standard | Grade |
|---|---|
| UNS | S31803, S32205 |
| EN | 1.4462 (X2CrNiMoN22-5-3) |
| Common name | 2205, duplex |
Equivalents are close, not identical. Name the grade and standard on the drawing.
Typical chemical composition
| Element | % |
|---|---|
| Chromium (Cr) | About 22–23 |
| Nickel (Ni) | About 4.5–6.5 |
| Molybdenum (Mo) | About 3–3.5 |
| Nitrogen (N) | About 0.14–0.20 |
| Carbon (C) | Up to 0.03 |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
Typical uses
- Chemical and petrochemical pipes, vessels and pumps
- Seawater and desalination equipment
- Oil and gas parts
- Pulp and paper plants
- Shafts and fasteners in corrosive service
Working with it
- Harder to machine than 316: lower speeds, rigid set-ups
- Welding needs controlled heat input and matching filler to keep the right structure
- Its high strength often allows thinner walls than 316
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Questions
- Is duplex 2205 better than SS316?
- For strength and chloride corrosion, yes: about twice the yield strength and much better resistance to pitting and stress corrosion cracking. It is harder to machine and weld.
- What is PREN?
- Pitting Resistance Equivalent Number, a quick guide to resistance to pitting in chlorides, calculated from chromium, molybdenum and nitrogen. Higher is better: about 24 for 316 and 35 for 2205.
- Is duplex stainless steel magnetic?
- Yes, partly, because about half of its structure is ferrite.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 15 October 2026.