Duplex stainless steels have emerged as optimal materials for desalination. Outokumpu, being the first to introduce the idea of solid Duplex evaporators, now offers DualDuplex™ for evaporators. In 1993, Outokumpu proposed the idea of solid Duplex evaporators. The benefits of Duplex are high strength combined with good to very high corrosion resistance depending on the grade. As a result, Duplex evaporators can be built with thinner plates, requiring less material and less welding. Further benefits include easier handling and less overall environmental impact. The breakthrough for Outokumpu’s Duplex concept came in 2003, when Outokumpu’s grade 2205 Duplex steel was selected for solid-Duplex evaporators to be installed in the Melittah MSF plant in Libya, built by Reggiane of Italy. The plant with 4 MIGD capacity was commissioned in 2004. In 2004 Outokumpu proposed a “DualDuplex™” concept – use of two different types of Duplex in the structures of evaporators – applying the highly corrosion resistant 2205 for parts exposed to the most hostile conditions, and Duplex LDX 2101® or Duplex 2304 for parts exposed to less hostile conditions. Currently three MSF plants are under construction by Fisia ItalimpiantI of Italy using Outokumpu’s DualDuplex™ concept, with a combination of 2205 and LDX 2101® from Outokumpu: Taweelah B, Jebel Ali L2, and Ras Abu Fontas B2, all to be completed in 2007-08. SIDEM of France is applying the DualDuplex™ concept using 2304 and 2205 from Outokumpu in the world’s largest MED plant to date, Al Hidd in Bahrain with 60 MIGD capacity, to be completed in 2007. Super-Duplex SAF 2507 is used in high-pressure piping and energy recovery units in seawater reverse osmosis plants, where very high corrosion resistance is essential to fight the hostile environments. Outokumpu supplies Duplex stainless steels for the majority of the world desalination plant contractors, in quarto plate, sheet, pipes and tubes.