applied fracture mechanics

Early Corrosion Fatigue Damage on Stainless Steels Exposed to Tropical Seawater:A Contribution from Sensitive Electrochemical Techniques 239takes place. This stage stops if repassivation of the micro-pit occurs. A volume of up toseveral m 3 of metal can be dissolved in stainless steel during the metastable growth. Insome cases the metastable pit growth precedes stable pitting. On the other hand, ifrepassivation of metastable micro-pit does not occur, the growth of stable pits can take place(figure 5).Figure 5. (a) AFM surface image and (b) Potential and current noise profiles for a 316L SS exposed tonatural seawater under an induced cyclic stress of = 140 MPa (58%0.2), after N=86400 cycles, at aload frequency ω=0.17 Hz and stress ratio R=0 [16].Measurements of the physical separation of anodic and cathodic areas, the currents flowingbetween them as well as the mapping of potentials in electrolytic solutions have beensuccessfully used for the study of the processes of localized corrosion of different systems[47-53]. A schematic drawing of a local corrosion cell is shown in figure 6.Figure 6. Schematic of current and potential distribution in solution during localized corrosion [40].