Effect of Heat Treatment on Corrosion and Stress Corrosion Cracking of S32205 Duplex Stainless Steel in Caustic Solution

Abstract

Duplex stainless steels (DSSs) have generally performed very well in caustic environments. However, some corrosion and stress corrosion cracking (SCC) of DSSs have been reported in different pulp mill environments employing caustic solutions. Studies have shown that the corrosion and SCC susceptibility of DSSs depend on the alloy composition and microstructure of the steel. In this study, the effect of a sulfide-containing caustic environment (pulping liquor) and material properties (DSS alloy composition and microstructure) on the corrosion and SCC of DSSs was evaluated. During metal fabrication processes, localized areas of DSSs may be exposed to different temperatures and cooling rates, which may lead to changes in the microstructure in these regions. This change in microstructure, in turn, may 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 S32205 DSSs in caustic environment was evaluated. The results showed that changes in the microstructure of S32205 DSSs due to selected heat treatments did not have a significant effect on the general corrosion susceptibility of the steel in caustic environment, but its SCC susceptibility varied with changes in microstructures.

Effects of Heat Input on Microstructure, Corrosion and Mechanical Characteristics of Welded Austenitic and Duplex Stainless Steels: A Review

“…Cracks were frequently prevented on extended, upright austenite grains, or overpass through [131]. The heat input did not influence the susceptibility to SCC.…”

Investigations Using Smooth and Notched Specimens into Validity of Caustic Cracking Susceptibility Diagram

“…However, it is important to note that the research programs for alumina and pulp-and-paper industries (where caustic cracking is a concern) have used both smooth and notched specimens. [9,15,16] It may be necessary to investigate the validity of the caustic cracking susceptibility diagram when smooth and notched specimens are tested, as reported in the current study.…”

Corrosion Behavior of Duplex and Lean Duplex Stainless Steels in Pulp Mill

“…In the pulp and paper industry, carbon steel pulp mill equipment, like digesters, storage vessels, have been showed general corrosion and stress corrosion cracking 14,[23][24][25] . Singh and Anaya evaluated the corrosion behavior of carbon steel (A 516-Gr 70), AISI 304 and 316 stainless steels, and two DSSs (UNS S32304, UNS S32205) in black liquor produced by pulping five wood species in a synthetic liquor.…”