Degradations of Type 422 stainless steel in aqueous environments

The susceptibility of Type 422 stainless steel (UNS S42200) to stress corrosion cracking (SCC) and localized corrosion was determined in neutral and acidic aqueous solutions at ambient and elevated temperatures. No failures were observed in the neutral solution at constant load. SCC testing by the slow-strain-rate technique revealed reduced ductility, time-to-failure and true failure stress due to the combined effect of elevated temperature and lower pH. These parameters were further reduced due to the cathodic charging. The localized corrosion studies using the cyclic potentiodynamic polarization technique showed pits and crevices in all specimens. Metallographic and fractographic evaluations showed secondary cracks along the gage section, and a combination of ductile and brittle failures at the primary fracture face of the tested specimen, respectively, depending upon the test environment.