Duplex Stainless 2205 is a nitrogen-enhanced duplex used in applications requiring high strength and excellent corrosion resistance. It is designed to combine improved resistance to stress corrosion cracking, pitting and crevice corrosion. Duplex 2205 provides nearly double the corrosion resistance typical in other austenitic stainless steels.

More useful information

• Duplex  stainless steels have a mixed microstructure of austenite and ferrite, the aim usually being to produce a 50/50 mix, although in commercial alloys the ratio may be 40/60. Duplex stainless steels have roughly twice the strength compared to austenitic stainless steels and also improved resistance to localized corrosion, particularly pitting, crevice corrosion and stress corrosion cracking. They are characterized by high chromium (19–32%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels.

The properties of duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. Duplex grades are characterized into groups based on their alloy content and corrosion resistance.

• Lean duplex refers to grades such as UNS S32101 (LDX 2101), S32304, and S32003.
• Standard duplex is 22% chromium with UNS S31803/S32205 known as 2205 being the most widely used.
• Super duplex is by definition a duplex stainless steel with a pitting corrosion equivalent (PRE) > 40, where PRE = %Cr + 3.3x(%Mo + 0.5x%W) + 16x%N. Usually super duplex grades have 25% chromium or more and some common examples are S32760 (Zeron 100 via Rolled Alloys), S32750 (2507) and S32550 (Ferralium),.
• Hyper duplex refers to duplex grades with a PRE > 48 and at the moment only UNS S32707 and S33207 are available on the market.

Comparison of standardized steels