316L vs Dúplex 2205
When 316L isn't enough — but nickel alloys would be overkill. Duplex 2205 fills the gap with double the strength and superior chloride resistance.
| Propiedad | 316L | Duplex 2205 |
|---|---|---|
| UNS | S31603 | S32205 |
| Microstructure | 100% austenite | ~50/50 austenite-ferrite |
| Tensile Strength | ≥ 485 MPa | ≥ 655 MPa (+35%) |
| Yield Strength | ≥ 170 MPa | ≥ 450 MPa (+165%) |
| Elongation | ≥ 40% | ≥ 25% |
| PREN | 24 – 28 | 34 – 38 |
| Critical Pitting Temp | 15 – 25°C | 40 – 50°C |
| Cl-SCC Resistance | Susceptible above 80°C | Immune up to 120°C |
| Max Service Temp | 800°C | 300°C (475°C embrittlement) |
| Density | 8.00 g/cm³ | 7.85 g/cm³ |
| Relative Cost | 1.0× (base) | 2.0 – 2.5× material / 1.2-1.5× project |
| Wall Thickness Saving | — | 30 – 40% vs 316L at equal pressure |
| NACE MR0175 | ≤ HRC 22, temp ≤ 60°C | ≤ HRC 28, temp ≤ 232°C |
450 MPa
2205 Yield (2.6× 316L)
PREN 35
Seawater Service Grade
1.2-1.5×
Project Cost vs 316L
Conclusion
El límite elástico 2.6× del dúplex 2205 significa paredes 30-40% más delgadas a la misma presión nominal. El material cuesta 2× más, pero el sobrecosto del proyecto es solo del 20-50% después de contabilizar menor material, estructuras más ligeras y soldadura reducida. Para offshore, desalinización y cualquier entorno con cloruros por encima de 1,000 ppm a temperatura elevada — el 2205 es la solución de costo óptimo entre el 316L y las aleaciones de níquel.
Preguntas Frecuentes
What chloride threshold separates 316L from duplex 2205?
316L has a PREN of about 25–26 and is generally limited to chloride around 1000 ppm at moderate temperatures, significantly less above about 60°C (140°F). Duplex 2205 (PREN about 34–36) tolerates far higher chlorides — often several thousand ppm — and resists pitting to a critical pitting temperature near 60–70°C. For seawater (roughly 19,000 ppm Cl-) or brackish duty, 2205 is the safer specification. TOKO TECH supplies both 316L and 2205 pipe and tube with PMI to confirm the actual PREN before shipment.
How much wall thickness and weight can 2205 save versus 316L?
Duplex 2205 has roughly twice the yield strength of 316L (about 450 MPa versus about 170–220 MPa). That lets designers cut wall thickness 25–40% for the same pressure, shrinking weight and footprint — critical for offshore topsides, skids, and shipbuilding where every kilogram counts. Thinner walls also lower thermal mass. TOKO TECH provides ASME B31.3 and B31.1 calculation support and EN 10204 3.1 MTCs so engineers verify the reduced wall meets allowable stress and code minimums.
Is 2205 more expensive than 316L after you account for wall reduction?
2205 mill price is roughly 1.8–2.2 times 316L per tonne, but because walls are 25–40% thinner the net installed cost is typically only 20–30% higher — and often lower once you add weight savings on supports, freight, and fabrication. In chloride-exposed or weight-sensitive projects the lifecycle cost strongly favors 2205. TOKO TECH models both options per line so buyers see true cost, not just unit price.
How do 316L and 2205 compare for stress corrosion cracking?
316L is vulnerable to chloride stress corrosion cracking (Cl-SCC), especially above about 60°C with tensile stress and chlorides — a common failure in warm, wet, chlorinated service. Duplex 2205 is far more resistant to Cl-SCC because of its ferritic phase, though it is not immune and must avoid the 250–350°C sensitization window. For hot chloride or coastal and industrial atmospheres, 2205 dramatically lowers SCC risk. TOKO TECH advises 2205 for any line above about 50–60°C with chlorides present.
What fabrication and welding controls does 2205 require?
2205 is weldable but demands control: use matching filler (ER2209), keep heat input moderate, and avoid the 250–350°C sensitization zone and intermetallic (sigma) phase formation above about 350°C. Post-weld heat treatment is generally not required if procedures are correct. 316L is far more forgiving to weld. For field fabrication with mixed crews, 316L reduces risk; for shop-built, qualified duplex procedures, 2205 is reliable. TOKO TECH supplies WPS and PQR references and qualified welder guidance for 2205 spools.
When should I choose 316L and when should I choose 2205?
Choose 316L for general, low-chloride, ambient-to-moderate service (food, pharma, indoor process) where cost and weldability dominate and Cl- stays below about 1000 ppm at temperature. Choose 2205 for seawater, brackish, offshore, desalination, pulp and paper, and any hot chloride or weight-critical line. Below about 1000 ppm and under 60°C, 316L is usually sufficient and cheaper. TOKO TECH helps EPCs set a chloride and temperature cutoff per service so neither is over- nor under-specified.