SERVICE EXPERIENCE WITH DUPLEX STAINLESS-STEELS IN THE CHEMICAL-INDUSTRY

The 22% Cr, 5% Ni and 3% Mo grade of duplex stainless steel is by far the most used duplex grade in the chemical process industry. Duplex steels have conquered a portion of about 6% of all highly alloyed materials used to combat corrosion in chemical industry. The main areas being chloride containing aqueous media with pH values not to low-duplex steels are used there for their high stress corrosion resistance. Other fields of application are hot caustic soda at relatively low temperatures where nickel or nickel base alloys can be replaced, and media where high nickel contents are unfavourable to the corrosion resistance. Some literature findings showing other possible fields of special application of ''standard'' 22/5/3 and also of so called superduplex grades are critically evaluated.