The Role of Interstitial and Substitutional Impurities in Stress Corrosion Cracking of Low Carbon Steel in Nitrate Solution Available to Purchase

The metallurgical aspects of the stress corrosion cracking of Fe-0.025% C in 5N NH₄NO₃ at 75 C (167 F) have been investigated. Sites of preferential corrosion in the alloy [annealed at 925 C (1697 F) and aged at 250 C (482 F)] were examined by transmission electron microscopy, and the susceptibility of the alloy to stress corrosion cracking after varying heat treatment was examined in constant strain rate tests. From the experimental data and calculated rate of transfer of impurities to and from grain boundaries, it was concluded that the tendency of grain boundaries to preferential corrosion is determined primarily by segregated substitutional constituents, and not by C or N.