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A line list that simply says 2205 can be filled against two different UNS numbers, and the older S31803 allows nitrogen as low as 0.08% where the newer S32205 starts at 0.14%, which changes how the welds behave and how much corrosion resistance they keep. Nitrogen is the difference. Duplex 2205 pipes and tubes to UNS S31803 give roughly twice the yield strength of 316L with far better chloride resistance. That combination thins the wall and keeps the line out of chloride stress corrosion cracking territory. They serve process, water and offshore systems across Oman. Related grades are on the duplex and super duplex hub.
Where Duplex 2205 (S31803) Is Used
- Seawater and brine-adjacent process piping
- Produced water and injection systems
- Desalination plant process lines
- Offshore topside utility and process systems
- Chemical and fertilizer plant lines with chlorides
The tightened modern version is duplex S32205; for more severe chloride service, super duplex 2507 goes further.
S31803 and S32205: Reading a 2205 Callout
Requirement | S31803 | S32205 |
|---|---|---|
Chromium | 21.0 to 23.0% | 22.0 to 23.0% |
Nickel | 4.5 to 6.5% | 4.5 to 6.5% |
Molybdenum | 2.5 to 3.5% | 3.0 to 3.5% |
Nitrogen | 0.08 to 0.20% | 0.14 to 0.20% |
Minimum tensile strength | 620 MPa | 655 MPa |
Minimum yield strength | 450 MPa | 450 MPa |
Nitrogen does two jobs in duplex steel: it adds strength, and it speeds the re-formation of austenite in a weld heat-affected zone as it cools. A heat at the bottom of the S31803 nitrogen range therefore leaves welds with more ferrite and less corrosion resistance than a S32205 heat would. Most modern specifications call for S32205, and many mills supply material dual certified to both. When a drawing simply says 2205, ask which UNS number the design assumed.
Corrosion, Phase Balance and Sour Service
Duplex performance depends on keeping roughly equal ferrite and austenite. Welding that cools too quickly leaves excess ferrite and lower corrosion resistance; holding the steel in certain temperature ranges precipitates intermetallic phases that embrittle it. Ferrite content checks on production welds are common. Under NACE MR0175 / ISO 15156-3, duplex grades are accepted within defined limits of H2S, chloride, temperature and pH, with a hardness limit that applies to pipe and welds. State your service conditions in the RFQ; requirements are confirmed at quotation.
Pricing Duplex 2205 (S31803) Pipe and Tube
- Raw material surcharges for the alloying elements in this grade
- Seamless or welded construction
- Diameter, wall thickness and cut lengths
- Required finish and cleanliness
- Testing, certification level and witness requirements
- Quantity and availability
- Incoterm and port of discharge
Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.
What to send for a quotation:
grade, standard, seamless or welded, NPS or OD, schedule or wall, length, quantity, finish, testing, the UNS number your design assumed, certification, inspection, destination port and required date.
Mill Certificates and Verification
Duplex 2205 (S31803) is supplied with EN 10204 3.1 certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. The certificate should record chemistry, heat treatment, tensile properties and any additional testing ordered. Positive material identification is worth specifying wherever several stainless grades share a fabrication shop. See the MTC and EN 10204 certification guide.
Storage and Contamination Control
Lead time is confirmed at quotation. Material is capped and, where specified, wrapped to protect the surface. Iron contamination is the main storage risk: carbon steel tools, slings and airborne grinding dust all leave particles that rust and can trigger pitting, so segregation on the Gulf laydown yard matters as much as the original grade choice.
Fittings and Related Grades
Match with ASTM A815 WP S31803 fittings and A182 F51 flanges.
Duplex 2205 is used across desalination and water treatment, marine and offshore and refinery and petrochemical plants.
Duplex 2205 (S31803) FAQ
What is the difference between S31803 and S32205?
S32205 has a higher nitrogen minimum (0.14% against 0.08%), a higher chromium and molybdenum floor, and a higher minimum tensile strength. Both are called 2205.
Does nitrogen matter in duplex?
Yes. It adds strength and helps austenite re-form in weld heat-affected zones, which preserves corrosion resistance.
Can material be dual certified to both?
Yes, where a heat meets both sets of limits. Many mills supply dual certified 2205.
How strong is 2205 compared with 316L?
Its minimum yield is 450 MPa against 170 MPa for 316L, which often allows a thinner wall.
What is the hardness limit?
290 HBW or 30 HRC maximum under ASTM A790.
What should I send for a quotation?
Send the UNS number, standard, form, size, wall, length, quantity, testing, certification, inspection and destination port.
Request a Quote for Duplex 2205 Pipes and Tubes (UNS S31803)
Send the UNS number, size, wall and quantity, with the piping specification attached. Every enquiry is checked before the offer is prepared, so a plain 2205 callout is resolved to a definite grade before material is ordered.