The Effect of Nitrogen on Stress Corrosion Cracking of AISI 304 Stainless Steel in High-Temperature Sulfate Solution

Slow strain rate tests (SSRTs) were conducted on solution annealed and sensitized AISI 304 stainless steels (SSs) with varying nitrogen and carbon contents to study their susceptibility to stress corrosion cracking (SCC). The tests were conducted in deaerated 0.1 M Na₂SO₄ at 250 C at a strain rate of 2 × 10⁻⁶/s and an applied potential of 0 V_H. For the sensitized SS containing 0.05 wt% carbon, susceptibility to intergranular stress corrosion cracking (IGSCC) decreased with nitrogen additions up to ~ 0.16 wt%. Scanning electron microscopy (SEM) showed that a transition from IGSCC to transgranular stress corrosion cracking (TGSCC) occurred at greater nitrogen contents. Potentiodynamic polarization curves measured in the above environment were identical for both the solution annealed and sensitized conditions, but the latter showed slightly greater current densities (CDs). Nitrogen additions had no influence on anodic polarization characteristics. No changes were noted in the polarization curves, which would explain or predict the observed SCC resistance.