Is S31803 the same as 2205?

When sourcing duplex stainless steel pipes, plates, or fittings, many procurement professionals encounter two commonly used designations: S31803 and 2205. These terms are often used interchangeably, but are they truly the same? Understanding the relationship and differences between these grades helps buyers make informed and cost-effective decisions.

 

What is S31803 material?
S31803 is a duplex stainless steel known for its high strength, excellent resistance to pitting and stress corrosion cracking in chloride environments, and a ~50/50 microstructure of ferrite and austenite. It is a standard duplex grade often referred to as 2205 or F51 and is used in chemical processing, oil and gas industries, and desalination plants due to these properties.

 

What is duplex 2205 material?

Duplex stainless steel 2205 (UNS S32205/S31803) is a commonly used, high-strength, duplex (austenitic and ferritic) stainless steel. Its composition includes 22% chromium, 3% molybdenum, and 5-6% nickel, providing excellent strength and fatigue resistance. It is widely used in the chemical, oil and gas, and marine industries, such as in storage tanks, pipelines, heat exchangers, and other high-pressure, corrosive environments.

 

Duplex stainless steel 2205 Chemical Composition

Element (%)	UNS S31803 / 2205 (Typical)
Chromium (Cr)	21.0 – 23.0
Nickel (Ni)	4.5 – 6.5
Molybdenum (Mo)	2.5 – 3.5
Nitrogen (N)	0.08 – 0.20
Carbon (C)	≤ 0.03
Iron (Fe)	Balance

 

duplex 2205 Mechanical properties

Property	Value
Tensile Strength (MPa)	≥620
Yield Strength (0.2% Offset, MPa)	≥450
Elongation (% in 50mm)	≥25
Hardness (Rockwell B)	≤29
Impact Strength (Charpy V-notch, J)	≥47 @ -46°C
Density (g/cm³)	7.8
Modulus of Elasticity (GPa)	200
Thermal Conductivity (W/m·K)	19
Coefficient of Thermal Expansion (10⁻⁶/°C)	13.7

 

Is S31803 the same as 2205?
Yes, they are essentially the same material. 2205 is a generic trade name, while S31803 is the UNS designation. An improved version of S31803, sometimes called UNS S32205, has slightly more stringent compositional controls, resulting in enhanced corrosion resistance.
S31803 and 2205 are used interchangeably in most procurement documents. When purchasing, please verify the applicable ASTM/EN standards and MTC (Mill Test Certificate) to ensure compliance. 

 

Duplex stainless steel 2205 Applications

Offshore oil & gas pipelines

Heat exchangers and pressure vessels

Marine engineering and desalination plants

Pulp & paper industry

Chemical processing equipment

 

What is the difference between S31803 and 316?
Compared with SS316, UNS S31803 will have around twice the yield strength. The Pitting Resistance Equivalent Number (PREN) of UNS31803 is close to 34, whereas it is 25 for SS316, meaning that its resistance to pitting corrosion is proportionally less.

 

What is the difference between uns S32750 and uns S31803?
The UNS S32750 fasteners show great resistance to localized corrosion and they can withstand stress corrosion cracking due to their high mechanical strength. In fact, the ASTM A276 Duplex Steel Uns S31803 Hex Bolts shows better corrosion resisting properties compared to the austenitic stainless steel.

 

With over 18 years of export experience and an annual supply of over 1,000 tons of duplex stainless steel, Gnee has become a trusted partner to various industries worldwide. Our S31803 (2205) duplex stainless steel pipes, plates, and fittings fully comply with ASTM, ASME, EN, and DIN standards. Available in outer diameters from 6 mm to 1,200 mm, with customizable thicknesses and lengths, we offer value-added services such as cutting, beveling, polishing, CNC machining, and welding. We also offer moisture-resistant treatment and export packaging in wooden crates and pallets.

Click here to get the S31803 (2205) duplex stainless steel material list