Duplex 2205 stainless steel (1.4462): properties, corrosion and applications

Duplex 2205 (1.4462) is a high-strength stainless steel that combines roughly double the proof strength of 304 with outstanding chloride and stress-corrosion resistance. Its dual austenitic-ferritic microstructure makes it the grade for marine, chemical and high-load structures where 316L is not enough. ULAMEX supplies duplex 2205 in sheet, plate, bar, profile and pipe, to EN 10088, with a 3.1 certificate on request. This guide covers the microstructure, composition, properties, corrosion behaviour and when to choose it.

What duplex stainless steel is

Duplex stainless steels have a two-phase microstructure of roughly equal parts austenite and ferrite. That mix is what gives duplex its defining advantage: the ferrite delivers high strength and resistance to chloride stress-corrosion cracking, while the austenite keeps the steel tough and formable. Grade 2205 (1.4462) is the workhorse duplex, named for its nominal 22 percent chromium and 5 percent nickel.

Compared with the austenitic grades 304 and 316L, duplex 2205 is stronger, more resistant to stress-corrosion cracking, and uses less nickel, while remaining weldable and fabricable. The trade-off is that it needs more care in welding and forming to keep the phase balance correct.

The duplex family: lean, standard and super duplex

2205 sits in the middle of the duplex range. Below it, lean duplex grades such as 2304 (1.4362) use less molybdenum for a lower-cost grade with moderate corrosion resistance. Above it, super duplex grades such as 2507 (1.4410), with around 25 percent chromium and higher molybdenum and nitrogen, reach a PREN above 40 for the most aggressive seawater and acid service. For the large majority of high-strength, high-corrosion applications, standard 2205 is the right balance of performance and cost, which is why it is the most widely used duplex grade and the one ULAMEX stocks as standard.

Chemical composition

The higher chromium, molybdenum and nitrogen of 2205, compared with 316L, are what drive its strength and corrosion resistance. Composition follows EN 10088-1.

Mechanical properties

The headline property of duplex 2205 is strength: its proof strength is roughly double that of 304 or 316L, which lets a designer use thinner, lighter sections for the same load. Values below are typical minimums to EN 10088-2; the exact figures appear on the EN 10204 3.1 certificate.

Corrosion resistance and PREN

Duplex 2205 resists localised corrosion better than the standard austenitic grades. Its Pitting Resistance Equivalent Number, PREN = Cr + 3.3 x Mo + 16 x N, is around 35, well above 316L, which gives it strong resistance to pitting and crevice corrosion in chloride environments.

Its biggest single advantage is resistance to chloride stress-corrosion cracking (SCC). Austenitic 304 and 316L can crack under the combination of tensile stress, chlorides and warmth, for example in warm seawater or process pipework; the ferritic phase in duplex makes 2205 far more resistant to this failure mode. That is why 2205 is specified for warm chloride service where austenitic grades are at risk.

Temperature limits and heat treatment

One important limit sets duplex apart from the austenitic grades: it is not for high-temperature service. Held in the 300 to 1000 degrees C range, duplex can form embrittling phases (475 degrees C embrittlement and sigma phase), so 2205 is generally limited to service temperatures up to around 250 to 300 degrees C. Where a stainless steel has to run hot, an austenitic grade such as 316Ti is the choice instead.

Duplex 2205 is supplied in the solution-annealed and quenched condition, heat treated at around 1020 to 1100 degrees C and rapidly cooled to fix the correct phase balance and dissolve any harmful phases. After welding or hot forming, the same control of cooling preserves the properties, which is why fabrication procedure matters more for duplex than for an austenitic grade.

Duplex 2205 versus 316L: when to choose it

316L covers most stainless work; duplex 2205 is the step up when strength, chlorides or stress-corrosion cracking push beyond what an austenitic grade can handle. For the full 304 and 316 picture, see our guide to 304 and 316 stainless steel.

Applications of duplex 2205

Duplex 2205 is the grade for demanding combinations of load and corrosion. Marine and offshore structures use it for its strength and seawater resistance; chemical and petrochemical plant uses it for tanks, pipework and pressure equipment in aggressive media; desalination and water treatment rely on its chloride resistance. In construction, 2205 suits structural components subject to high mechanical loads and chloride-induced stress-corrosion cracking, such as coastal bridges, pool-hall structures and facade supports in marine atmospheres. The higher strength also allows weight and material savings against an austenitic design.

Design and cost advantages

The high strength of 2205 is a design tool. Because its proof strength is roughly double that of 304 or 316L, a designer can specify thinner walls and lighter sections for the same load, which saves weight and material on tanks, structures and pressure equipment. Over the life of a marine or chemical asset, the better corrosion resistance also reduces maintenance and replacement.

On raw-material cost, duplex carries less nickel than the austenitic grades, so its price is less exposed to nickel-price swings. The combination of lower nickel content, weight savings from higher strength and long service life often makes 2205 competitive on whole-life cost even where its price per kilogram is higher than 316L.

Welding and fabricating duplex 2205

Duplex 2205 is weldable, but it needs more control than an austenitic grade to keep the ferrite-austenite balance and avoid harmful intermetallic phases. The usual filler is a 2209 type (over-alloyed in nickel) to restore austenite in the weld. Heat input and interpass temperature are controlled, and the steel should not be held too long at high temperature. With correct procedure, welded duplex retains its strength and corrosion resistance; ULAMEX operates EN 1090-1 EXC2 and ISO 3834-2 for structural fabrication, and the 3.1 certificate confirms the delivered properties.

Forming and machining duplex

Beyond welding, duplex 2205 fabricates well but demands more power than an austenitic grade. Its high strength means higher forming forces and more springback when bending, so press tools and bend allowances are set accordingly. Machining is slower than for 304 or 316L because of the higher strength and work hardening, so sharp tooling, positive feeds and rigid set-ups give the best result. None of this prevents standard workshop fabrication; it simply means planning the cut, bend and weld sequence around the grade.

Forms and product range

ULAMEX supplies duplex 2205 across the forms a fabrication or construction job needs: sheet and plate, round, flat and square bar, profiles, and tube and pipe, with fittings where required. Sheet and plate cover tanks, vessels and cladding; bar and profile cover structural members and machined parts; tube and pipe cover process and marine pipework. All are supplied to EN 10088 with a 3.1 certificate on request. For duplex and austenitic sheet specifically, see our guide to stainless steel sheet.

Inspection and quality

Because the properties of duplex depend on the ferrite-austenite balance, quality control focuses on that balance. The ferrite content is held in a controlled range, broadly 35 to 65 percent, and can be measured on the finished part; impact testing confirms toughness, and a corrosion test can verify pitting resistance for critical service. ULAMEX supplies duplex 2205 with an EN 10204 3.1 inspection certificate on request, confirming composition and mechanical properties, batch-traceable per shipment, so the delivered material matches the specification.

Duplex 2205 from ULAMEX

ULAMEX supplies duplex 2205 (1.4462) alongside the austenitic and ferritic grades, as part of a stainless range built for fabrication and construction. Stock and supply cover sheet and plate, bar, profile and tube and pipe.

Need duplex 2205 for a project? Send the form, dimensions and quantity, and ULAMEX will return a non-binding quotation with availability, lead time and pricing. Browse the full stainless steel range, or contact the export desk at [email protected] or +48 504 424 761. For our full range, certification and quote process, see steel and aluminium supply capabilities.

Frequently asked questions