514

exposure to exfoliation corrosion, Kt = 2.5

exposure to exfoliation corrosion, Kt = 2.5

decreases significantly. In addition, the discussed material embrittlement is diffusion controlled. Thus, large components with small amounts of free edges are expected to suffer less from obtained material embrittlement. Yet, locally (e.g., in the area of neighboring rivets where multiple-site damage (MSD) and widespread fatigue damage (WFD) may be developed as well) corrosion-induced embrittlement may become significant. Further investigation is needed to quantify whether the observed fatigue resistance drop due to corrosion may be explained solely by the presence of corrosion notches, which are reducing the fatigue crack initiation phase significantly, or may be related to determined ductility drop as well.

9.6.3.4 Hydrogen Characterization

The pattern of hydrogen evolution, with heating of the corroded specimen, has been shown to depend strongly on temperature. A plot of hydrogen concentration in the purge stream versus temperature is shown for some representative cases in Fig. 9.25. Different curves correspond to specimens with varying exposure time to the exfoliation solution. Multiple peaks are observed and are attributed to different trapping states.

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