Duplex and Superduplex stainless steel grades for wet flue gas desulphurisation systems

The corrosion risks in a wet flue gas desulphurization system environment are reported. Uniform and localized corrosion resistance of different stainless steels is studied by electrochemical tests. The effects of chloride content, fluoride content, pH and temperature on corrosion resistance are discussed. The results show that duplex UNS S32205 or superduplex UNS S32520 grades are prime substitutes for austenitic 317LNM or super austenitic like UNS S34565 grades in many aggressive environments. The life cycle costs of scrubbers constructed of stainless steels plates or clad plates are compared. The excellent corrosion resistance of duplex and superduplex stainless steels, combined with their increased mechanical properties and moderate alloy cost afford very cost effective solutions for wet flue gas desulphurization.