Intergranular Stress Corrosion Cracking of Sensitized Type 304 Stainless Steel in Sodium Sulfate at Approximately 100°C

The susceptibility of sensitized type 304 (UNS S30400) stainless steel to intergranular stress corrosion cracking (IGSCC) was studied in constant load tests and slow strain rate tests using flat tensile specimens in 0.01 M Na₂SO₄ at 50 to 125° C. At 125°C, IGSCC susceptibility was prominent in the middle of the passive range and the critical potential for IGSCC (E_crit) was close to the passivation potential, which was consistent with previous results at 150°C. At 100 and 75°C, however, IGSCC was observed in the transition potential range from the active to the passive state. Despite the lack of IGSCC in the gauge section in the potential range above the passive state, crevice corrosion generated around the pinhole caused failure of the specimen at 100° C. In the corresponding potential range below 75° C, no failure was obtained. The cracking behavior is discussed mechanistically in terms of the nature of films, dissolution, hydrolysis, and repassivation of the metal.