X2CrNiMoN22-5-3 · S31803 / S32205 · Duplex 2205 · EN 10253-2 Type B
Standard duplex stainless steel. PRE ≥35. 2× the yield strength of 316L. NACE MR0175 compliant for sour gas service. The dominant grade for offshore, subsea, and chloride-aggressive process piping where 316L falls short.
Duplex stainless steels have a two-phase austenite-ferrite microstructure (approximately 50/50 by volume). This delivers three simultaneous advantages over purely austenitic grades like 316L: higher yield strength (≥450 MPa vs ~220 MPa for 316L), higher pitting resistance (PRE ≥35 vs ~24 for 316L), and much better resistance to chloride stress corrosion cracking (SCC). The SCC immunity comes from the ferritic phase interrupting propagation pathways.
The higher strength means wall thickness can be reduced relative to 316L for the same pressure rating — partially offsetting the material cost premium. In offshore piping, the combined corrosion + strength performance of duplex 2205 makes it the default over either CS (corrosion) or 316L (insufficient strength and chloride resistance) for topside and subsea chloride environments.
| Element | Min | Max | Role |
|---|---|---|---|
| Carbon (C) | — | 0.030% | Low C — weldability |
| Chromium (Cr) | 21.0% | 23.0% | Passivation, PRE contribution |
| Nickel (Ni) | 4.5% | 6.5% | Austenite stabiliser |
| Molybdenum (Mo) | 2.5% | 3.5% | Pitting resistance (PRE) |
| Nitrogen (N) | 0.10% | 0.22% | Austenite stabiliser + PRE |
PRE = %Cr + 3.3×%Mo + 16×%N. Typical PRE ≥35 for 1.4462.
| Property | 316L (1.4404) | Duplex 2205 (1.4462) | Super Duplex (1.4410) |
|---|---|---|---|
| PRE | ~24 | ≥35 | ≥40 |
| Yield strength | ~220 MPa | ≥450 MPa | ≥530 MPa |
| Chloride SCC resistance | Poor | Good | Excellent |
| NACE MR0175 | Conditional | Yes (hardness cert) | Yes (hardness cert) |
| Max service temp | ~300°C | ~300°C | ~300°C |
| Sigma phase risk | Low | Above 300°C | Above 280°C |
| Filler | ER316L | ER2209 | ER2594 |
Above approximately 300°C, sigma phase (σ) can precipitate in duplex stainless steels, causing severe embrittlement. This restricts duplex 2205 to process temperatures below 300°C. For piping systems that cycle through higher temperatures (e.g. steam purge, CIP/SIP in pharmaceutical), confirm that the peak temperature never exceeds this limit. At ambient chloride service temperatures, duplex is unrestricted.
| EN number | 1.4462 |
| EN designation | X2CrNiMoN22-5-3 |
| UNS | S31803 / S32205 |
| PRE (min) | ≥35 |
| Yield strength | ≥450 MPa |
| NACE MR0175 | Compliant |
| Max service temp | ≤300°C |
| Filler (GTAW) | ER2209 |
| PWHT | Not required |
| Standard | EN 10253-2 Type B |
| Certificate | EN 10204 3.1 standard |
NACE MR0175 hardness certificate. EN 10204 3.1 standard. 3.2 (Lloyd's / BV / DNV) available for offshore. PMI on every duplex order.
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