ABSTRACT
The sea water resistance of members of the duplex family of UNS S32304, S31803 and S32750 is very different. UNS S2304 should not be used in sea water and UNS S31803 has roughly the same corrosion resistance as AISI904L. Finally, there is the superduplex stainless steel UNS S32750, with a similar resistance to austenitic 6Mo-steels. A 'super' stainless steel here refers to a high alloy stainless steel with a PRE (PRE = Cr + 3.3Mo + 16N) of more than 40. The superduplex UNS S32750, 25Cr-7Ni-4Mo, has a PRE of minimum 41. It has now been in service for more than 10 years. Extensive experience of using SAF 2507 in different environments has been gained. Experiences of the use in sea water of the three duplex stainless steels UNS S32304, S31803 and S32750 are summarised in this paper and instructions for good practice are given. Results are also given from an exposure of butt-welded tubes exposed in natural sea water. No significant corrosion was found on the samples included in this test.
