Duplex Stainless Steel 2205: Properties and When to Use It
Duplex 2205 stainless steel explained: austenite-ferrite structure, strength, PREN, chloride and stress corrosion resistance, welding and uses in desalination and oil and gas.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: Duplex 2205 (UNS S32205/S31803, EN 1.4462) is a stainless steel with a roughly 50/50 austenite-ferrite structure. It has about twice the yield strength of 316L and much better resistance to chloride pitting and stress corrosion cracking, making it common in desalination, seawater systems, chemical tankers and oil and gas.
Where 316L is not enough but nickel alloys are too expensive, duplex stainless steels fill the gap. Grade 2205 is the most widely used.
Composition (typical)
- Chromium ~22%
- Nickel ~5–6%
- Molybdenum ~3%
- Nitrogen ~0.15–0.2%
Key properties
| Property | 316L | Duplex 2205 |
|---|---|---|
| Min. yield (plate) | ~170 MPa | ~450 MPa |
| Approx. PREN | 24–26 | 34–36 |
| Stress corrosion cracking resistance | Moderate | High |
| Magnetic | No | Yes |
Advantages
- Higher strength allows thinner walls and weight savings
- Better chloride pitting resistance than 316L
- High resistance to chloride stress corrosion cracking, a common failure mode of austenitic grades in hot chloride environments
- Lower nickel than 316L, which can help price stability
Typical applications
- Desalination plants (evaporators, piping, tanks)
- Seawater-cooled heat exchangers
- Oil and gas process equipment and pipelines
- Chemical storage tanks
- Pulp and paper equipment
- Structural uses in aggressive environments
Limitations
- Upper temperature limit (around 250–300 °C) due to embrittlement risks
- Not suitable for very low temperature without qualification
- Welding requires care with heat input and filler (e.g. 2209)
Saudi relevance
With one of the world's largest desalination sectors and major coastal industrial clusters, duplex grades are widely specified in Saudi water and energy projects (water and desalination).
Specifying
Order to ASTM A240 (plate/sheet), A790 (pipe) or EN 10088 with the grade, finish and testing such as ferrite content and corrosion tests where required.
See our stainless steel range and 304 vs 316.