1000

O Air (5 Hz) • 0.6 M NaCl (1 Hz) 0 -1250 mV (vs SCE) (1 Hz)

105 106 Number of Cycles to Failure

FIGURE 11.14 S-N curve for high-strength steel in 3.5% NaCl solution (after [29]).

105 106 Number of Cycles to Failure

FIGURE 11.14 S-N curve for high-strength steel in 3.5% NaCl solution (after [29]).

One of the most notable features when comparing the in-air and corrosion fatigue resistance of a material is the loss of the fatigue or endurance limit for tests conducted in an aggressive environment. Figure 11.14 shows that fatigue failure continues to occur despite a reduction in the applied stress range to 70% of the in-air fatigue limit stress range. In addition, it can be seen that some restoration of fatigue strength occurs on applying a cathodic potential (CP), thereby eliminating the damaging anodic dissolution reaction that leads to pitting and early crack initiation.

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