Does duplex stainless steel rust? Corrosion
As with all corrosion resistant alloys, duplex stainless steels 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, SAF2205, 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.