2205 Duplex Stainless Steel
A duplex (ferrite + austenite) stainless steel, the most common of its type
Typical values for the temper in the title
2205 is a duplex stainless: its structure is about half ferrite and half austenite. This combination, with about 22% chromium, 3% molybdenum and nitrogen, gives it a yield strength roughly twice that of 316L and better resistance to pitting (PREN about 35) and stress corrosion cracking.
It is the common choice when 316L is not strong enough or fails in chlorides: chemical tanks and piping, desalination plants, marine structures and oil and gas. Thanks to its strength, thinner walls can be designed. The older version, S31803, is defined with wider ranges.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 620–880 MPa | |
| Yield strength Rp0.2 | 450–620 MPa | |
| Elongation A | 25% | |
| Hardness | 270–290 HB | |
| Modulus of elasticity E | 200 GPa | |
| Density ρ | 7.82 g/cm³ | |
| Machinability | 40% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Cr chromium | 22.0–23.0 (S31803: 21.0–23.0) | corrosion resistance |
| Ni nickel | 4.5–6.5 | balances ferrite and austenite |
| Mo molybdenum | 3.0–3.5 (S31803: 2.5–3.5) | pitting resistance |
| N nitrogen | 0.14–0.20 (S31803: 0.08–0.20) | strength, resistance and austenite stability |
| C carbon | max 0.030 | |
| Mn manganese | max 2.00 | |
| Si silicon | max 1.00 | |
| Fe iron | balance |
Ranges per ASTM A240 (plate and sheet), the same in A789/A790 for tubing.
Conditions and heat treatment
Duplex is supplied solution annealed and rapidly cooled, to get a structure of about half ferrite and half austenite.
| Condition | Properties | When to choose it |
|---|---|---|
| Solution annealed | yield roughly twice that of 316L | the normal delivery condition |
| Not hardenable by heat treatment | — | strength comes from the two-phase structure and nitrogen |
| Range to avoid | prolonged exposure at about 300–1000 °C forms brittle phases | so the upper service limit is about 250–300 °C |
Applications
- Chemical tanks and piping
- Desalination plants
- Marine structures and platforms
- Oil and gas industry
- Heat exchangers
Fabrication
Welding
Welds well, with a nickel-overalloyed filler (usually ER2209), so the weld has enough austenite. Keep heat input controlled, and check the ferrite content of the weld.
Machining
Harder than 316L because of the high strength. Sharp tools, low speeds and a steady feed.
Corrosion
Excellent resistance to chloride stress corrosion cracking, where ordinary austenitic stainless is weak.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 316 / 316L | 485–620 / 170–310 MPa | Excellent — ER316L | cheaper, weaker and less resistant · material page |
| 2507 Super Duplex | 795–900 / 550–680 MPa | Good — ER2594 | super duplex: more resistant, for harsh conditions · material page |
| 2304 | 600-750 / 400-450 MPa | Good | lean duplex: cheaper, almost no molybdenum · material page |
Common mistakes
Using duplex above about 300 °C
With prolonged exposure, brittle phases form. For heat, austenitic stainless.
Welding with matching (not overalloyed) filler or uncontrolled heat
The weld may be ferrite-rich, brittle and less corrosion resistant.
Ordering "2205" without stating S32205 or S31803
The ranges differ, and many specifications require the tighter S32205. State it explicitly.
Equivalents, standards and supply
| EN | 1.4462 |
|---|---|
| DIN | X2CrNiMoN22-5-3 |
| JIS | SUS329J3L |
| Standards | ASTM A240 / EN 10088-2 / NACE MR0175 |
| Forms | plate · rod · pipe |
| Producers | Outokumpu · Sandvik SAF 2205 · Acerinox · Valbruna |
Learn more
Values are typical and for comparison only. For design, rely on the standard and on the mill certificate. Sources: ASTM A240, ASTM A276 and EN 10088 (composition), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026