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 st eels have conquered a portion of about 6% of all highly alloyed materi als used to combat corrosion in chemical industry. The main areas bein g chloride containing aqueous media with pH values not to low-duplex s teels are used there for their high stress corrosion resistance. Other fields of application are hot caustic soda at relatively low temperat ures where nickel or nickel base alloys can be replaced, and media whe re high nickel contents are unfavourable to the corrosion resistance. Some literature findings showing other possible fields of special appl ication of ''standard'' 22/5/3 and also of so called superduplex grade s are critically evaluated.