Environmental corrosion-fatigue cracking

It is often difficult to conduct laboratory tests in which both the environmental and stressing conditions approximate to those encountered in service. This applies particularly to the corrosive conditions, since it is necessary to find a means of applying cyclic stresses that will also permit maintenance around the stressed areas of a corrosive environment in which the factors that influence the initiation and growth of corrosion fatigue cracks may be controlled. Among these factors are electrolyte species and concentration, temperature, pressure, pH, flow rate, dissolved oxygen content and potential (free corrosion potential or applied). 

Figure 7.13. Types of corrosion (environmentally affected) fatigue crack growth response...

Subcritical Crack Growth Environmentally Assisted Fatigue Crack Growth (or Corrosion Fatigue)... 

Banford, W.H., Jacko, R.J., Wilson, I.L.W., Ceschini, L.J. The effect of material and environmental variables on corrosion fatigue crack growth in pressure vessel steels. NRC NUREG/CP-0058 4 (1984)... 

General description. In incomplete fusion, complete melting and fusion between the base metal and the weld metal or between individual weld beads does not occur (Fig. 15.8). Incomplete fusion that produces crevices or notches at surfaces can combine with environmental factors to induce corrosion fatigue (Chap. 10), stress-corrosion cracking (Chap. 9), or crevice corrosion (Chap. 2). See Fig. 15.9. 

---