Duplex Steel
Duplex stainless steel 1.4462 (UNS S31803, also known as 2205) is the workhorse of the duplex family: a dual-phase austenitic–ferritic microstructure delivering roughly double the yield strength of standard 316.
1.4462 is used across chemical processing, offshore and marine, oil and gas, water treatment, pressure vessel fabrication, heat exchangers and structural applications where standard 316L would need to be heavier or wouldn't survive the service environment.
Its controlled chromium, molybdenum and nitrogen chemistry gives it excellent resistance to a wide range of chloride, acidic and marine media at a materially lower price point than super duplex grades.
Duplex Stainless Steel
The Duplex structure offers roughly twice the yield strength of standard austenitic stainless steels, while maintaining good ductility and toughness. It also provides outstanding resistance to stress corrosion cracking, pitting and crevice corrosion, particularly in chloride-containing environments.
-
UNS 31803 - 1.4462​
UNS S31803 / 1.4462 delivers a proven combination of mechanical performance and corrosion resistance. It contains controlled levels of chromium, molybdenum and nitrogen, giving it excellent resistance to a wide range of chemical and marine environments.
This makes S31803 / 1.4462 a dependable and cost-effective choice for critical applications where durability and reliability are key.
Duplex Steel Applications
The superior strength and corrosion resistance of Duplex stainless steel sheet and plate make it suitable for use across a wide range of sectors. It is widely utilised in chemical processing, oil and gas, offshore and marine, and water treatment industries, as well as in structural, pressure vessel and heat exchanger fabrication.
​
Its high mechanical strength allows for thinner sections and lighter fabrications, helping to reduce material and fabrication costs without compromising on performance.
​
Typical applications include storage tanks, pressure vessels, piping systems, desalination plants, architectural supports, and marine components where strength and corrosion resistance are paramount.
Why Duplex Steel
Compared with 304L or 316L, Duplex stainless steel offers significantly higher strength and superior corrosion resistance, particularly in chloride-bearing environments. This allows for lighter and more durable designs with extended service life and reduced maintenance.
​
Compared to higher-alloyed Super Duplex grades, standard Duplex stainless steel such as UNS S31803 / 1.4462 delivers excellent all-round performance at a more accessible cost.
It is easier to fabricate and weld than Super Duplex, yet still provides the enhanced corrosion protection and mechanical strength required for many industrial and structural applications.
Frequently Asked Questions
What is duplex stainless steel?
Duplex stainless steel has a mixed microstructure — approximately 50% austenite and 50% ferrite — which gives it roughly twice the yield strength of standard austenitic stainless steels like 316L while also improving chloride pitting resistance and stress corrosion cracking resistance. 1.4462 (UNS S31803) is the most widely specified duplex grade worldwide.
​
What's the difference between duplex and super duplex stainless steel?
Duplex (1.4462) has a Pitting Resistance Equivalent Number (PREN) around 34–35. Super duplex grades (1.4501, 1.4410) have PREN above 40, giving them significantly better resistance to chloride pitting and crevice corrosion in aggressive marine and subsea environments. Super duplex is more expensive and harder to fabricate.
When should I choose duplex over 316L?
When you need higher strength (to reduce section thickness and weight), better chloride resistance (for marine or brackish water service), or better stress corrosion cracking resistance. Duplex often works out cheaper than 316L overall on a strength-per-tonne basis because you use less material.
What UNS number is 1.4462?
UNS S31803. It's also known as 2205 (its two-phase composition, 22% chromium 5% nickel) and by its EN designation 1.4462.
Do you stock duplex stainless steel in the UK?
Yes. European-origin plate and sheet, cut to size at our Lancashire processing facility.
Steel Dynamics UK stocks 1.4462 in plate and sheet from leading European mills, cut to size and shipped nationwide under ISO 9001 and ISO 19443.
It is also easier to fabricate and weld than super duplex, which is why buyers reach for 1.4462 first and only step up when the service environment demands it.
