Technical knowledge
Duplex 2205 vs 316L: the cost case, not just the corrosion case
A practical comparison of duplex 2205 and 316L for piping and flanges: strength, corrosion limits, wall thickness saving, fabrication cost and the conditions where 316L remains the correct choice.
The numbers that drive the decision
| Item | 316L | Duplex 2205 |
|---|---|---|
| Yield strength | 170 MPa minimum | About 450 MPa |
| Typical PREN | About 26 | 35 - 38 |
| Chloride stress corrosion cracking | Susceptible above about 60 C | Highly resistant |
| Recommended metal temperature | Broad, including cryogenic to about 800 C | About minus 50 to 300 C |
| Welding familiarity | Very high | Requires control |
| Magnetic | No | Yes |
Where 316L is still the correct choice
- Low chloride, moderate temperature. If the chloride content and temperature are genuinely low, the duplex premium buys nothing.
- Very high temperature. Above the duplex limit, 316L or a stabilised grade remains applicable.
- Cryogenic service. Austenitic stainless retains toughness at very low temperature where duplex does not.
- Thin section, heavily formed parts. Austenitic grades are more forgiving in severe forming operations.
How to compare installed cost properly
- Price the pipe and flanges by metre or by joint, not by kilogram, after applying the wall thickness permitted by the higher allowable stress.
- Include the weight effect on supports, hangers and transportation.
- Add the welding cost difference: duplex needs a qualified procedure, controlled heat input and often ferrite and impact testing.
- Subtract the expected maintenance and replacement cost over the plant life for the credible failure modes.
Tip Ask your supplier for a per joint price comparison rather than a per kilogram comparison. The answer often reverses once wall thickness is applied.
Questions about this topic
Is duplex 2205 harder to weld than 316L?
It requires more control but it is not difficult. Use an over alloyed filler, keep heat input within the qualified range, control interpass temperature, and verify ferrite and impact properties as the specification requires.
Does duplex 2205 resist chloride stress corrosion cracking?
Yes, far better than any austenitic stainless steel. This is one of the main reasons it replaced 316L in warm seawater, brine and produced water service.
Why is duplex magnetic and does it matter?
The ferrite phase is magnetic. It matters for identification, for certain instrument installations and where magnetic particle inspection is planned, but it has no effect on corrosion performance.
Questions about our products
What products does Hangbo Alloy supply?
Four product families, all available in nickel-based alloys, titanium, duplex and special stainless steel: flanges, butt weld pipe fittings, elbows, and seamless tube and pipe. Flanges cover weld neck, long weld neck, slip-on, blind, socket weld, threaded and lap joint patterns. Fittings and elbows cover concentric and eccentric reducers, equal and reducing tees, caps, stub ends, and 45°, 90° and 180° returns in both long and short radius, plus 3D and 5D bends for piggable lines. Seamless tube and pipe is supplied cold drawn or hot finished from 6 mm to 630 mm outside diameter.
Which alloy grades are available for these products?
More than 90 grades are published in our grade library. The most requested are Inconel 625, 718, 600 and X-750, Hastelloy C-276, C-22 and B-2, Monel 400 and K-500, Incoloy 800H, 825 and 925, duplex 2205 and super duplex 2507, 316L, 904L and 254SMO stainless steel, and titanium Grade 2 and Grade 5. Nickel-based grades can also be supplied with VIM plus ESR double melting where cleanliness or fatigue life is critical.
What sizes, wall thicknesses and pressure classes can you supply?
Flanges run from NPS ½ to NPS 24 to ASME B16.5 and from NPS 26 to NPS 60 to ASME B16.47 Series A or B, in pressure classes 150 through 2500. Butt weld fittings and elbows run from NPS ½ to NPS 48 (DN 15 to DN 1200) in wall thickness Schedule 5S through XXS. Seamless tube and pipe covers 6 mm to 630 mm outside diameter, in random lengths of about 5 to 7 metres or fixed lengths up to 12 metres. Non-standard and intermediate sizes are quoted on request.
Which material and dimensional standards do you work to?
Forged flanges to ASTM B564, B381 and A182 with dimensions to ASME B16.5 and ASME B16.47. Butt weld fittings and elbows to ASTM B366 and A403 with dimensions to ASME B16.9 and MSS SP-43. Seamless tube and pipe to ASTM B444, B423, B622, B163, B167, B861, A312, A213 and A790. Marking follows MSS SP-25 and the applicable product standard. If your project is governed by EN, DIN, JIS or a company specification, send the document and we will confirm equivalence before quoting.
Is there a minimum order quantity?
There is no minimum for standard sizes and grades held in stock, and prototypes, spares and small trial batches are accepted. Made-to-order melts and special forgings carry a minimum weight that depends on the alloy and the route, typically from about 500 kg for special grades.
What inspection and certification is issued with the goods?
Every shipment carries an EN 10204 3.1 mill test certificate quoting the actual chemical and mechanical results for the specific heat lot, together with dimensional records and heat treatment data where applicable. Testing is carried out in house by optical emission spectrometry, tensile, impact and hardness testing, plus ultrasonic and eddy current examination, with hydrostatic pressure and intergranular corrosion testing to ASTM G28 or A262 Practice E where the specification requires it. Third party inspection by SGS or another recognised agency can be arranged, and their report is issued alongside the shipment.
What are typical lead times?
Standard stock items ship within days. Common production grades such as Inconel 625 or duplex 2205 are typically a few weeks. Special chemistries, larger forgings and items that require third party inspection take longer and are quoted individually against the requirement.
How are the products packed for export?
Flanges and fittings receive a rust preventive coating, are individually wrapped and are packed in plywood cases secured with steel banding. Tube ends are capped and bundles are strapped. Packing lists quote heat numbers so every case can be cross-checked against the mill certificate on arrival. We quote EXW, FOB, CFR, CIF and DAP, and mixed-alloy orders can be consolidated into one shipment with a single documentation package.
How do I request a quotation or a sample?
Send the grade or UNS number, the dimensions including schedule or wall thickness, the governing material and dimensional standards, quantity, any heat treatment or NDT scope and the certificate type you need; a drawing is ideal for special flanges and fittings. Email [email protected] or message us on WhatsApp +86 15618279078 and we normally issue a formal quotation within 24 hours on working days. Samples and previous test reports can be arranged before the first order.
Talk to an engineer
Share your duty conditions and we will shortlist candidate alloys within one working day.