Duplex 2205 Tubing (UNS S31803 / S32205)

Duplex 2205 tubing is OD-sized, round instrumentation tube drawn from 22Cr duplex stainless steel S31803 / S32205 (UNS S31803 original, S32205 nitrogen-enhanced; EN / W.Nr. 1.4462), a nominal 22Cr-5Ni-3Mo-N grade with a roughly 50/50 ferrite-austenite microstructure and a Pitting Resistance Equivalent Number around 35. It carries process fluid or gas between components and seats into a compression fitting's ferrule set to make a leak-tight, make-and-break joint. Crestflo supplies 2205 tube seamless and welded to ASTM A789, in both imperial and metric sizes, shipped in the solution-annealed condition so it bends and cones cleanly into a ferrule. You reach for 2205 tube when a line carries chlorides, brackish or produced water, or moderate sour (H₂S) fluid and the run also has to carry pressure at a lighter wall than 316 allows, the workhorse-duplex duty where 316 stainless pits and stress-corrosion-cracks, but where super duplex is more alloy than the service needs. Standard items ship from stock; specials are built to order, with delivery running 6-8 weeks. Request a quote to price your run.

Reviewed by the Crestflo Engineering Team

SAF™ 2205 is a trademark of Alleima (formerly Sandvik). Swagelok® and Parker® are trademarks of their respective owners; Crestflo is not affiliated, and interchange is dimensional.

Why Specify Duplex 2205 Tubing

Tube is the long, continuous wetted surface of an instrument hookup. Unlike a fitting or a valve, it has no dead legs or packing bores, but it has length, every inch of it exposed to the media, and it has to survive the cold work of bending and ferrule make-up without cracking. On a chloride line that rules out ordinary austenitic stainless. A tube that pits or stress-corrosion cracks midway along a run is as dead as one that fails at the fitting.

Duplex 2205 is a nitrogen-bearing duplex stainless steel, and its two-phase austenite-plus-ferrite structure is what makes it the right tube for chloride and moderate-sour service. Two properties drive the choice. First, corrosion: with a PREN near 35, 2205 resists chloride pitting and crevice corrosion well beyond 316L (≈24), and its duplex structure gives it strong resistance to chloride stress-corrosion cracking, the failure mode that limits austenitic stainless in warm chloride and brine. Second, strength: the grade's minimum yield is roughly double that of annealed 316/316L, and on a tube that is a direct, bankable advantage. A thinner wall holds the same pressure, so a 2205 run weighs less and costs less metal than a 316 run of the same rating, which matters on long instrument, hydraulic, and sample runs.

Be precise about where 2205 sits, though. It is the leaner, lower-alloy duplex, a step up from 316, not a stand-in for super duplex. Its PREN of about 35 trails Super Duplex 2507's >42, so its chloride ceiling is lower: 2205 handles seawater well at ambient temperature, but for hot seawater, aggressive subsea, and the harshest sour service, 2507 is the step up, not 2205. Where the duty is chloride-bearing process, brine at ambient, moderate sour service, and a strength advantage over 316, 2205 is the cost-effective answer and 2507 is over-specified. Don't carry 2205 past its chloride ceiling on the strength of its yield number.

There is one temperature limit to respect. Duplex 2205 is not a high-temperature grade. Continuous service is generally capped at about 600 °F (315 °C); hold it in the 600-1830 °F (315-1000 °C) band for any length of time and sigma-phase and 475 °C embrittlement degrade the grade's toughness and corrosion resistance. Its ferrite content also rules it out of cryogenic duty. Where a line runs hot, an austenitic nickel alloy such as Inconel 625 or Hastelloy C-276 is the pick, not 2205; where a line runs deep-cold, an austenitic grade like 904L is the better choice. Keep 2205 in the chloride, moderate-sour, and high-strength window where it excels.

The full metallurgical picture, composition ranges, mechanical and physical properties, PREN, and corrosion-by-media data, lives on the Duplex 2205 alloy grade page. This page stays on the tube: how it's made, sized, finished, tested, and matched to the fitting.

Also Specified As: 2205 Seamless Tube, UNS S31803 Tube, S32205 Instrument Tube

Buyers and specifiers call this tube several ways, and each one points to the same 22Cr duplex stainless. A requisition might read "Duplex 2205 tubing," "2205 duplex seamless tube," "S31803 instrument tube," "S32205 instrumentation tubing," "grade 2205 tube," or "22Cr duplex tube," and every one of them lands here. The formal designations are UNS S31803 (the original 2205) and UNS S32205 (the modern, nitrogen-enhanced version), plus EN / Werkstoff 1.4462 (EN steel name X2CrNiMoN22-5-3). A tube labeled "2205" today is almost always certified to both UNS numbers at once. SAF™ 2205 is Alleima's (formerly Sandvik's) trade name for the same grade, referenced here for identification only. The welded form is often written "welded-and-drawn tube," the seamless form "cold-drawn seamless tube."

Scope: this is round, OD-sized instrumentation and fluid-system tube for compression and tube-fitting connections. It is not oilfield coiled tubing for downhole well intervention, not structural or ornamental tube, and not pipe specified by nominal pipe size (NPS) and schedule. Crestflo supplies 2205 in instrumentation tube, fitting, and valve forms only, not mill bar, sheet, plate, or pipe.

Seamless vs Welded Duplex 2205 Tubing

Both constructions accept a compression fitting the same way, and for duplex tube both fall under a single product-form specification, ASTM A789, which covers seamless and welded ferritic-austenitic (duplex) stainless tubing for general service. That is one of the ways duplex tube differs from austenitic stainless and the nickel alloys, which split across separate seamless and welded standards. Seamless 2205 tube is cold-drawn from a hollow with no longitudinal weld, which makes it the default where you want maximum integrity for higher-pressure, cyclic, or critical sour service. Welded-and-drawn 2205 tube is formed from strip, seam-welded, then cold-drawn to size; it is dimensionally consistent and cost-effective for general instrument and fluid-system work. On a duplex, the weld and the following solution anneal and quench have to restore the ferrite-austenite balance across the seam and heat-affected zone, which is why the annealing and the ferrite check below matter as much as the chemistry.

Not sure which construction to call out? The deep dives on seamless tubing and welded tubing walk through the trade-off before you commit a spec.

Duplex 2205 Tube Attributes at a Glance

Duplex 2205 Tube Sizes: OD, Wall & Imperial/Metric

Instrument tube is specified by its actual outside diameter and wall thickness, given in both imperial and metric units, never by NPS and schedule. The common instrument range runs fractional 1/8″ to 1″ and metric 6 to 12 mm; smaller 1/16″ (3 mm) small-bore tube and larger diameters up to 2″ (50 mm) are available to order. Wall thickness is chosen to carry the pressure and to suit the ferrule, and both OD and wall are held to the tolerances of ASTM A789. This is where 2205's strength pays off directly: because the grade's allowable stress is well above austenitic stainless, a given pressure can be carried on a thinner wall, so the designer can trade some of the wall back for weight and cost on a long run. Working pressure is not a single blanket figure, though; it is calculated from OD, wall thickness, and the alloy's allowable stress per ASME B31.3, so it is stated per size and wall rather than as one rating for the grade.

Values per applicable standard; customizable to requirement. For how to work back from a target pressure to a wall thickness, see the tube sizing and wall thickness guide, and for the full dimensional matrix across the range, the tubing size chart.

Temper & Ferrite Balance: Solution-Annealed for Bending and Ferrule Seating

The single most important mechanical property of instrument tube is not its peak strength but its workability. 2205 tube ships in the solution-annealed and quenched condition, and on a duplex that condition does three jobs at once. First, it is what lets the tube bend around a radius and cone down under a ferrule without cracking, so the joint seats and seals the way a compression fitting is designed to. Second, it sets the ferrite-austenite phase balance near the target 50/50: a correct solution anneal followed by a rapid quench dissolves intermetallic phases and fixes the right ratio, and if the quench is too slow or the anneal off-temperature, the tube can carry excess ferrite or sigma phase that costs it toughness and corrosion resistance. Third, the solution-annealed condition is the one NACE MR0175 / ISO 15156 works from for sour service, with hardness held to the ≤ 31 HRC ceiling. In that condition 2205 still carries high strength, a 0.2% yield around 65 ksi (450 MPa), roughly twice annealed 316, with a tensile minimum near 90 ksi (620 MPa) and elongation at or above 25%. Because the phase balance is load-bearing on a duplex, every lot gets a ferrite check (see testing, below). Specify the hardness or condition to your own standard on the RFQ and it is confirmed on the certificate.

Finishes & Cleanliness: Bright-Anneal, Pickle, Electropolish & Oxygen-Clean

Duplex 2205 tube ships in a mill/bright-annealed or pickled finish as standard. For high-purity gas, analytical, and oxygen service, passivation, electropolishing (EP), and oxygen/UHP cleaning with capped-and-bagged packaging are available. Electropolishing lowers surface roughness and smooths the inner diameter, which matters where particle generation, moisture dry-down, or deposit build-up is the concern; on a chloride line a clean, smooth surface also removes the crevices and embedded iron where pitting likes to start. Standard UHP electropolish surface-roughness targets can be specified right on the RFQ to your own standard; electropolished tubing and oxygen and UHP cleaning cover the options in detail. Finish and cleanliness figures follow the applicable standard and are customizable to requirement.

Duplex 2205 Tube Standards: ASTM A789, A790, NORSOK & ASME B31.3

2205 tube is covered by the duplex stainless tube specification, not the austenitic-stainless or nickel-alloy ones: both seamless and welded tube fall under ASTM A789, with its matching ASME boiler-code SA-789 designation. The companion pipe specification, ASTM A790, covers S31803 / S32205 pipe, which is outside Crestflo's instrumentation tube scope and is noted only for reference. Allowable working pressure for a given size and wall is calculated per ASME B31.3. For offshore work, the NORSOK M-630 material data sheets and the related NORSOK M-650 manufacturing-qualification standard apply, and for sour service the material is offered to NACE MR0175 / ISO 15156. Crestflo holds the standard approvals that apply to instrumentation tube and is ISO 9001 / 14001 / 45001 and PED certified.

Working Pressure: Calculated per ASME B31.3, Not Assumed

There is no single pressure rating for "2205 tube," and any supplier who quotes one is skipping the engineering. Allowable internal pressure depends on three things: the tube OD, its wall thickness, and the alloy's allowable stress at the service temperature. ASME B31.3 sets the method, relating wall thickness to pressure, diameter, the allowable stress value S, the weld-joint quality factor E, and the coefficient Y. Seamless tube carries a higher joint factor than welded, which is part of why seamless is chosen for higher-pressure work. Duplex 2205's edge in this calculation is its high allowable stress, roughly twice that of austenitic 316 near room temperature, which is what lets a thinner wall carry the same pressure. That advantage holds up to the grade's service ceiling; above about 600 °F (315 °C) the material is off the table on toughness grounds, not just on allowable stress. Give us the OD, wall, temperature, and medium on the RFQ and the engineering team returns the calculated working pressure for your configuration. Values per the applicable standard; customizable to requirement.

Testing, Ferrite Check, NDT & NACE MR0175 Sour-Service Compliance

Every length of 2205 tube is verified before it ships. ASTM A789 requires each tube to pass either a hydrostatic test or a nondestructive (eddy-current) electric test, and dimensional checks confirm OD, wall, and straightness against the ordered tolerances. Because this is a duplex, the ferrite-austenite phase balance is checked as well, by metallographic point count or magnetic measurement, to confirm the microstructure sits in the specified band rather than running ferrite-heavy or carrying intermetallic phase from an off-anneal. Positive material identification (PMI) confirms the alloy on the material, which matters for a duplex where chemistry controls the phase balance and the corrosion performance. NDT is done in-house; destructive testing, where a job calls for it, goes to ISO/IEC 17025-accredited labs, and third-party inspection is available on request.

For sour service, 2205 tube material is offered to NACE MR0175 / ISO 15156, with hardness controlled to the ≤ 31 HRC ceiling the standard sets for duplex stainless. Confirm the hardness and the environmental limits, H₂S partial pressure, temperature, and chloride content, in the standard against your application, and note the sour-service requirement on the RFQ.

Straight Lengths & Coiled Duplex 2205 Tube

2205 tube ships as straight lengths for racked and rigidly supported runs, and as continuous coils for long analyzer and sample lines, chemical-injection cores, and tracing and hydraulic bundles where a joint-free run is the whole point. On a long chloride-service run the 2205 coil earns its keep twice over: it keeps the count of mechanical joints down, which on a brine or buried line is one fewer place to leak, and its high strength lets the core run thinner-walled, which trims weight and metal cost across a long bundle. Both forms are supplied solution-annealed and quenched; call out length or coil length on the RFQ. For long-run applications, see coiled tubing; for thicker-wall high-pressure control lines, hydraulic tubing.

Material Traceability & Certification

Every length of Duplex 2205 tube carries its own heat/lot number, and each order ships with an EN 10204 MTC 3.1 certificate as standard, 3.2 available on request. PMI confirms the grade at the part level, every time, and the ferrite check backs it with the microstructure data a duplex job needs. That documentation supports the audit trails that offshore, chemical, seawater, and sour-service work demand, the kind of job where a mis-specified or off-balance tube in a long run is an expensive thing to discover in commissioning. Full detail is on the traceability page.

Applications for Duplex 2205 Tubing

2205 tube earns its place wherever chlorides and chloride-SCC defeat 316, and the run also needs more strength than an austenitic can give, but the duty doesn't yet justify a super duplex:

• Upstream & offshore topside oil & gas, platform instrument, hydraulic, and produced-water lines in chloride and moderate-sour service, where chloride-SCC resistance and high strength both count. See the oil & gas industry page.
• Seawater & brine handling (ambient), cooling and process lines in ambient chloride service; step up to 2507 where the seawater runs hot.
• Desalination & RO (ambient), high-chloride brine instrument and sample lines on seawater desalination plant at ambient temperature.
• Pulp & paper, bleach-plant and chloride-laden process instrument and sample lines.
• Petrochemical & chemical process, chloride-bearing process, sampling, and flue-gas desulfurization instrument lines, and dilute-acid service where 2205 often beats 316L. See chemical processing.
• Marine & shipboard systems, high-chloride instrument and sample lines.

Where the chloride duty gets severe, hot seawater, aggressive subsea, or the harshest sour service, step up to Super Duplex 2507 tube; the full trade-off is in 2205 vs 2507. Where the line runs hot, an austenitic nickel alloy such as 625 or C-276 is the call, which 2205 cannot match above its 600 °F ceiling.

Pairing 2205 Tube With 2205 Fittings and Valves

A tube is one part of the hookup, and the joint is only as corrosion-resistant as its weakest metal. For a matched instrument run, pair this tube with Duplex 2205 tube fittings and Duplex 2205 instrumentation valves so the whole assembly, tube, ferrules, and valve body, carries the same PREN, the same strength, and the same traceability. Crestflo supplies the tube alongside compression fittings tested to ASTM F1387, so the ferrule set seats correctly on the exact OD and wall you ordered, and the joint is a dimensional match rather than a mix of two suppliers' tolerances. Putting a 2205 tube into a 316 fitting just moves the failure point to the ferrule.

Drop-In Interchange and the Tube-Plus-Fitting System

Crestflo 2205 tube is cut and finished to standard OD and wall, so it drops into the compression fittings you already run, and the matching 2205 fittings are built as dimensional interchange / equivalent parts for the major brands, with the fitting ends qualified to ASTM F1387. These are not "compatible" or "intermix" parts. Swagelok® and Parker® remain trademarks of their respective owners, and Crestflo is not affiliated; the interchange is strictly dimensional. Moving a run off a major brand? Request your Swagelok®/Parker® cross-reference and the engineering team maps your tube and fitting part numbers to Crestflo 2205 equivalents. We don't publish a part-number table.

Origin & US-Serving Positioning

Crestflo manufactures for the US market. Standard product is of Indian origin; US or European melt is available on request, with full material traceability. Tube is engineered as a US drop-in and ships in 6-8 weeks, well under the 20+ weeks typical of the majors. If a project calls for a specific melt origin or TAA/DFARS handling, specify it on the RFQ and we'll address it straight, no hedging. See the US-origin compliance page for how we document it.

Why Crestflo for Duplex 2205 Tubing

Crestflo operates as the instrumentation division of an export house with four decades behind it and formal recognition from the Government of India, with a proven Middle-East delivery record. That backing grounds a focused instrumentation brand built on a handful of clear advantages:

• Lead time of 6-8 weeks versus 20+ weeks typical of the majors, on standard stock and made-to-order specials alike.
• A matched system, tube plus F1387-tested fittings and ferrules that seat on the exact OD and wall you ordered.
• Both seamless and welded 2205 tube to ASTM A789, in both imperial and metric, straight or coiled.
• Heat-number marking plus MTC 3.1/3.2 on every order, PMI-confirmed and ferrite-checked, so a duplex is never taken on trust.
• NACE MR0175 / ISO 15156 material options for sour service, hardness controlled ≤ 31 HRC, with NORSOK M-630/M-650 for offshore work.
• ISO 9001 / 14001 / 45001 & PED certified, cost-competitive after US duties and tariffs, with small MOQs and private-label available.

We Engineer Confidence.

Request a Quote for Duplex 2205 Tubing

Give us the details: seamless or welded, OD and wall, straight length or coil, finish and cleanliness, and the line conditions (media, pressure, temperature, sour-service requirement). We'll calculate the working pressure, confirm the spec, and schedule the run.

• Request a quote, the fastest path to pricing and lead time.
• Request a sample for qualification.
• Request your Swagelok®/Parker® cross-reference and we'll map your tube and fitting part numbers.

Datasheets and CAD are available to customers on request. Reach Crestflo's US sales desk at sales@crestflousa.com or +1 346 594 9005 (Houston, TX). Round out the system with 2205 tube fittings and 2205 valves, browse the tubing pillar for other grades and constructions, and see where this tube serves in oil and gas.

Frequently Asked Questions

Related Pages

• Duplex 2205 alloy grade & corrosion data
• Duplex 2205 tube fittings · Duplex 2205 instrumentation valves
• Tubing pillar · Seamless tubing · Welded tubing · Alloy tubing
• Super Duplex 2507 tubing · 2205 vs 2507
• ASTM A789 · ASME B31.3 · NACE MR0175 · EN 10204 MTC
• Oil & gas instrumentation · chemical processing