​​​​​​​​​​​​​​​​​​​​​​​​​​Duplex, lean duplex and super duplex stainless steels –
twice as strong as austenitics 


Outokumpu duplex stainless steels offer an excellent combination of strength and corrosion resistance, meaning you can significantly reduce material thickness and cost in a host of applications.

Our duplex innovation is unmatched in the industry and our offering covers a full palette of duplex stainless steels for use in diverse industries and applications. 

The high mechanical strength of duplex grades is a result of the duplex microstructure and the alloying with nitrogen. This high strength gives opportunities for reducing both weight and cost as a thinner material can be used. Low nickel content of the duplex grades makes them price stable.

The duplex grades LDX 2101® and 2304 are referred to as lean duplex grades. Typical applications are storage tanks, bridges, water heaters and reinforcement bars. The corrosion resistance is comparable to the standard austenitic grades like 4301 and 4404 respectively or high alloyed ferritics like 4521.

Grades 2507 and 4501 are regarded as super duplex grades. They are highly alloyed and have a corrosion resistance comparable to high performance austenitics like 254 SMO®. Typical applications for super duplex are desalination plants, seawater systems, flue-gas cleaning, umbilicals, storage tanks and pressure vessels.

By lowering total material weight, you also lower transportation and assembly costs, reducing environmental impacts even further – making duplex stainless steel a genuine material of the future.  

Put our expertise to work for you.
Check Stainless steel finder to browse available grades, product forms and dimensions and surface finishes by product form.
Contact Outokumpu sales to discuss more


​​Product properties

Duplex grades have a ferritic-austenitic microstructure, with a phase balance of approximately 50% ferrite and 50% austenite. Duplex grades combine many of the beneficial properties of ferritic and austenitic stainless steels. The duplex microstructure contributes to the high strength and high resistance to stress corrosion cracking.

Other characteristic properties of duplex grades include good abrasion and erosion resistance, good fatigue resistance, high-energy absorption and low thermal expansion.

For more information

  • Open the Downloads tab to download Outokumpu duplex stainless steel datasheets
  • View all technical specific​​ations online including mechanical properties, chemical composition, physical properties and corrosion characteristics

Compare technical specifications for all Outokumpu steel grades



Duplex stainless steels generally have good weldability and can be welded using most of the welding methods used for austenitic stainless steels:

  • Shielded metal arc welding (SMAW)
  • Gas tungsten arc welding TIG (GTAW)
  • Gas metal arc welding MIG (GMAW)
  • Flux-cored arc welding (FCW)
  • Plasma arc welding (PAW)
  • Submerged arc welding (SAW)
  • Laser welding
  • Resistance welding
  • High-frequence welding

For more information


 Corrosion resistance

Duplex stainless steel grades are superior to standard austenitics with regard to stress corrosion cracking resistance, and duplex grades are also good in a number of acidic and alkaline environments.

Outokumpu's duplex offering is unique: for a given austenitic stainless steel grade there is a duplex counterpart that not only provides similar corrosion resistance but also twice the strength.

For more information

  • Open the Downloads tab to download the Outokumpu duplex stainless steel datasheet
  • Check Steel Finder to find information about PRE (Pitting Resistance Equivalent), CPT (Critical Pitting Temperature) and CCT value (Critical Corrosion Temperature)
  • Check the Online Corrosion Table and search by chemical name or formula corrosion rates for stainless steel grades
  • Find an Outokumpu sales office near you to get the printed version of the Outokumpu Corrosion Handbook




Shows the list of publications in the main column




Outokumpu stainless steel strengthens Lossendammen dam locks in Swedenhttp://www.outokumpu.com/en/stainless-news/cases/outokumpu-stainless-steel-strengthens-lossendammen-dam-locks-in-swedenOutokumpu stainless steel strengthens Lossendammen dam locks in SwedenThomas FunkeSales Manager, Outokumpu PSC Outokumpu plate service center advised the contractor on the advantages of stainless steel in this project. The benefits for the customer were weight saving, easier transportation and maintenance.
Outokumpu stainless used in Siena Bridge, Italyhttp://www.outokumpu.com/en/stainless-news/cases/outokumpu-stainless-used-in-siena-bridge-italyOutokumpu stainless used in Siena Bridge, ItalyPierangelo PistolettiSETECOMild steel poses a risk for critical structures, because without regular coating the structures can be attacked by serious corrosion, leading to material fatigue and even to a risk of collapse.
Duplex for Europe's longest pedestrian and cycling bridgehttp://www.outokumpu.com/en/stainless-news/cases/duplex-for-europes-longest-pedestrian-and-cycling-bridgeDuplex for Europe's longest pedestrian and cycling bridgeRonny SödergrenStål & Rörmontage ABWe can avoid repainting costs associated with the bridge arches and rails every 15th year.

Over 100 years of technical expertise to the challenges faced by our customers today

Our commitment to technical innovation and the development  of new grades for new applications is found in our extensive R&D labs in Finland, Sweden and Germany. 

We also show technical expertise in manufacturing of stainless steel using more than 80% of recycled material in production. 

Contact our local experts to solve your material problems

Sustainable stainless steel

​The most efficient ways to reduce the overall environmental impact is raising the input of recycled steels and recovered metals - more than 80% of Outokumpu stainless comes from recycled content. 

Read more