Yes. As with all corrosion-resistant alloys, duplex stainless steels can suffer corrosion when exposed to sufficiently corrosive conditions. Because they contain more chromium than standard 3xx grades, their Pitting Resistance Equivalent Number (PREN) is higher, indicating greater resistance to pitting corrosion.

For example, the PREN for a duplex stainless steel (Sanmac^® 2205, SAF2205, 1.4462, F51/F60, S31803, S32205) is 34, while that for Alloy 316L (1.4404, S31603) is only 25. That is an appreciable increase in resistance to pitting corrosion.

Frequently asked questions

Can duplex stainless steel rust?

Yes. Like all corrosion-resistant alloys, duplex stainless steel can corrode when exposed to sufficiently aggressive conditions. It contains more chromium than standard 3xx grades, though, which gives it a higher PREN and greater resistance to pitting corrosion.

How much more pitting-resistant is duplex than standard 316L?

Sanmac 2205 duplex has a PREN of 34, compared with just 25 for Alloy 316L. That is an appreciable increase in resistance to pitting corrosion, reflecting duplex's higher chromium content relative to standard austenitic grades.

Why does chromium content matter for pitting resistance?

Chromium is one of the key elements in the pitting resistance equivalent number (PREN) calculation, so a higher chromium content directly raises PREN. That is why duplex grades, with more chromium than standard 3xx stainless steels, resist pitting corrosion better.

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