applied fracture mechanics

Early Corrosion Fatigue Damage on Stainless Steels Exposed to Tropical Seawater:A Contribution from Sensitive Electrochemical Techniques 245Figure 12. Amount of dissolved material per pit, determined from the chronoamperometries and by amethod of material removal as a function of anodic polarization time for the 304 SS in a) naturalseawater and b) 3.5% wt NaCl solution [55].Figure 13. SRET map scans during pitting initiation and growth on 304 SS specimens polarized at 290mV vs SCE for 2.3, 17.5, 37.5 and 56.5 minutes under fatigue loading conditions [40].Figure 14. Pits formed at grain boundaries of a 316L SS undergoing cyclic loading in natural seawater. = 140 MPa (58%0.2), after N=86400 cycles, at a load frequency ω=0.17 Hz, stress ratio R=0, TAve=29C and pHAve = 7.9. Patterns of grain boundaries are reveled practically in the image [56].Acuña [56] has observed that on the maximum tensile stress zone of bent-beam specimens,after N loading cycles in natural seawater, the pits nucleation sites generally were located atgrain boundaries on the specimen surface (Figure 14).