Abstract
Duplex stainless steels (DSS) have generally performed very well in the pulp mill environment. However, some corrosion and stress corrosion cracking (SCC) of duplex stainless steels has been reported in different pulping liquors. Studies have shown that corrosion and SCC susceptibility of duplex stainless steels depend on alloy composition, microstructure and temperature. In this study the effect of sulfide containing caustic environment (pulping liquor) and material properties (DSS alloy composition and microstructure) on the corrosion and SCC of DSS in pulping liquors (synthetic white liquor) was evaluated. During metal fabrication processes, localized areas of DSS may be exposed to different cooling rates or aging temperatures, which may lead to a change in the microstructure or produce precipitates in these regions. This change in microstructure may in turn affect the general and localized corrosion or SCC susceptibility of the affected area as compared to the rest of the metal. Hence the effect of different annealing and aging temperatures as well as cooling rates on the microstructure and corrosion behavior of 2101 and 2205 DSS in pulping liquors was evaluated. 2205 and 2304 welded DSS specimens were tested for SCC susceptibility in pulping liquor. Reduction in molybdenum content in welded 2304 DSS specimens did not seem to provide any protection against SCC as compared to 2205 DSS.
