SAF 2507 or UNS S32750 (25Cr-7Ni-4Mo-0.30N) is a high alloy superduplex stainless steel and has now been in service for nearly 10 years. It has excellent resistance to localised corrosion in chloride-bearing environments. This has been proven by laboratory tests, exposure tests in natural seawater and field experiences. During the years results have shown that SAF 2507 has roughly the same or better corrosion resistance when compared to the 6Mo steels.

Long term exposures tests of butt-welded tubes in seawater Swedish West Coast has been performed. For the weld exposed for six years a corrosion rate of only 0,005 mm/year were found. In the base material no general corrosions was found. SAF 2507 and 6Mo showed the same resistance. This has also been the result in large crevice corrosion programs in Europe. In natural seawater SAF 2507 has even performed almost as well as 7Mo. In the paper design curves for SAF 2507 in seawater are shown and recommendations based on these are discussed. For example, practical experiences during the years in intermittent chlorinated seawater suggests a maximum allowed temperature as high as 60°C for tube walls. For chlorination it is recommended to use intermittent chlorination of 2 ppm 2 times a day for 30 minutes. In these cases a flow rate of minimum 1 m/s is required. For crevices under such conditions the maximum temperature suggested is 40°C.

For instance in order to avoid galvanic corrosion when coupling the steel to other materials is discussed, cathodic protection could be used. If following good practice no difficulties with hydrogen embrittlement should appear.