An Overview of Duplex Stainless Steel

A duplex stainless steel is named because it has a ‘duplex’ microstructure, meaning a balance of austenitic and ferritic grains. This means that duplex stainless steels combine the physical and mechanical properties of both, making them an attractive and cost-effective proposition. Commonly used for applications in multiple industries including marine, oil, gas and wastewater treatment.

Does Duplex Stainless Steel Rust?

In simple terms, duplex stainless steel does have a high corrosion resistance. The first duplex stainless steels were based around 22% chromium content, which provides significantly better corrosion resistance compared with a more standard Alloy 316L austenitic stainless steel. In addition, the strength is up to twice that of 316L as well. 

With that said, duplex stainless steel and other corrosion-resistant alloys can suffer corrosion when exposed to suitably corrosive conditions. As they contain a higher chromium content than standard 3xx grades, their Pitting Resistance Equivalent Number (PREN) is higher, indicating increased resistance to pitting corrosion.

For instance, the PREN for a duplex stainless steel (Sanmac 2205, SAF 2205, 1.4462, F51/F60, S31803, S32205) is 34, whilst that for Alloy 316L (1.4404, S31603) is only 25. Therefore, an appreciable increase in resistance to pitting corrosion can be expected.

Got Any Questions? Get in Touch With Us Today

Langley Alloys is a UK and US-based supplier of duplex stainless steel bars and plates. Available in various sizes to suit your requirements. If you would like to receive a quotation, or if you have any other questions about duplex stainless steel and its corrosion resistance properties, please get in touch with us today.


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