S31803 Duplex Stainless Steel Sheet Plate Corrosion Resistance
S31803 plate is a duplex stainless steel grade defined under UNS S31803, corresponding to EN 1.4462 and commonly known as Duplex 2205. It features a balanced austenitic-ferritic microstructure (approximately 50% austenite / 50% ferrite), delivering approximately twice the yield strength of standard austenitic grades like 304L or 316L, combined with excellent resistance to chloride stress corrosion cracking (SCC), pitting, and crevice corrosion.
S31803 is one of the original duplex stainless steel specifications and remains widely used in chemical processing, oil & gas, marine, and desalination applications where both high strength and superior corrosion resistance are required.
Key Features
| Feature | Description |
|---|---|
| Microstructure | Austenitic + Ferritic (≈50/50 dual-phase) |
| Yield Strength | ≥450 MPa (~2× stronger than 316L) |
| PREN | ~35 (excellent pitting resistance) |
| Corrosion Resistance | Superior against SCC, pitting, crevice corrosion |
| Temperature Range | -50°F to 600°F (-46°C to 316°C) continuous service |
| Magnetic | Yes (due to ferrite phase) |
| Weldability | Good with proper procedures |
Equivalent Designations
| Standard | Grade |
|---|---|
| ASTM | UNS S31803 |
| EN | 1.4462 |
| AISI | 2205 |
| JIS | SUS329J3L |
| DIN | X2CrNiMoN22-5-3 |
| ISO | 2205 |
Note: UNS S32205 is a newer specification with tighter composition ranges. S31803 remains acceptable for many applications but may have slightly broader allowable ranges for chromium (21.0-23.0% vs 22.0-23.0%) and molybdenum (2.5-3.5% vs 3.0-3.5%).
Specifications & Size Range
| Parameter | Range |
|---|---|
| Thickness | 0.3 mm – 100 mm (custom up to 200 mm available) |
| Width | 50 mm – 3500 mm |
| Length | 1000 mm – 12000 mm (custom available) |
| Standard Coil Widths | 1000 mm, 1219 mm, 1240 mm, 1500 mm, 2000 mm |
| Standard | ASTM A240 / A480, ASME SA240, EN 10088-2, JIS G4304/G4305 |
Surface Finishes
| Finish | Code | Characteristics | Application |
|---|---|---|---|
| No.1 | Hot rolled, annealed & pickled | Original industrial surface | Pressure vessels, industrial equipment |
| 2B | Cold rolled, bright finish | Smooth, reflective | General fabrication, tanks |
| BA | Bright annealed | Mirror-like reflectivity | Decorative applications |
| No.4 | Brushed | Matte, fine satin finish | Architectural, food processing |
| HL | Hairline | Continuous linear streaks | Building facades, elevators |
| 8K | Mirror | Highly reflective | Luxury decorative finishes |
S31803 vs. S32205 Comparison
| Feature | S31803 | S32205 |
|---|---|---|
| Chromium (Cr) | 21.0 – 23.0% | 22.0 – 23.0% |
| Molybdenum (Mo) | 2.5 – 3.5% | 3.0 – 3.5% |
| Nitrogen (N) | 0.08 – 0.20% | 0.14 – 0.20% |
| PREN (typical) | 32 – 38 | 35 – 38 |
| Property Consistency | Broader range | Tighter control |
| Status | Original specification | Modern preferred spec |
S32205 offers tighter composition control and more consistent properties. However, S31803 remains widely accepted and readily available in the market.
Corrosion Resistance Highlights
| Corrosion Type | Performance |
|---|---|
| Pitting / Crevice | PREN ~35 → excellent resistance in chloride environments; far superior to 304/316 |
| Stress Corrosion Cracking (SCC) | Highly resistant to chloride and H₂S environments; NACE MR0175 compliant for sour service |
| General Corrosion | Superior to 304/316 in organic acids (formic, acetic) and dilute sulfuric acid |
| Intergranular Corrosion | Low carbon content prevents sensitization |
| Seawater Resistance | Excellent; widely used in seawater systems |
Processing Guidelines
Hot Working
Temperature range: 1750 – 2050°F (950 – 1120°C), followed by rapid cooling (water quenching). Avoid working below 1700°F (925°C).
Cold Working
Requires approximately 30-50% higher forming force compared to 316L. Intermediate annealing may be required for severe deformation.
Heat Treatment
-
Solution Annealing: 1870 – 2010°F (1020 – 1100°C)
-
Cooling: Water quench or rapid air cool
-
Hardening: Not hardenable by heat treatment; only through cold working
Welding
-
Suitable with standard methods (SMAW, GTAW, GMAW, SAW, FCAW)
-
Recommended filler metal: 2209 (E2209 or ER2209)
-
Control heat input (0.5 – 2.5 kJ/mm) to maintain phase balance
-
Preheat is generally not required
-
Post-weld heat treatment is not typically needed
-
Avoid overheating to prevent intermetallic phase precipitation
Machining
Requires rigid tooling and lower cutting speeds due to higher strength and work hardening tendency.
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