Pitting behavior of lean duplex stainless steels in thiosulfate-containing paper machine environments

摘要

This paper examined the pitting corrosion resistance of new grades of lean duplex stainless steels (LDSSs) UNS S32304, UNS S32003 and UNS S82441 in both chloride-only solution and thiosulfate containing simulated white water environments. Potentiodynamic cyclic polarization tests showed that thiosulfate increased pitting susceptibility mainly through lowering repassivation potential. Both potentiodynamic cyclic polarization tests and scratch tests revealed that LDSSs with higher molybdenum content, i.e. UNS S32003 and UNS S82441, were more corrosion resistant than UNS S32304 in thiosulfate-containing environment and preferential dissolution of the ferrite phase was observed in UNS S32304 specimens after tests in thiosulfate-containing solution. The understanding of how different grades of stainless steels behave in thiosulfate containing environments not only helps with material selection, but also contributes to the understanding by which thiosulfate ions affect pitting in different alloys.