Corrosion fatigue experimentation

Electrode potential should be monitored and, if appropriate, maintained constant during corrosion fatigue experimentation. Apparent effects of variables, such as the dissolved oxygen content of the solution, flow rate, ion concentration, and alloy composition on corrosion fatigue, can often be traced to dianging electrode potential. 

Prior to the 1960s, stress corrosion cracking and corrosion fatigue were principally under the purview of corrosion chemists and metallurgists, and the primary emphasis was on the response of materials in aqueous environments (e.g., sea/salt water), particularly for SCC because of the relative ease of experimentation. Much of the attention was devoted to the understanding of electrochemical reactions that are associated with metal dissolution, crack nucleation, and time-to-failure under a... 

Thomas, J. P., and Wei, R. P., Corrosion Fatigue Crack Growth of Steels in Aqueous Solutions - I. Experimental Results Modeling the Effects of Frequency and Temperature, Matls. Sci. Engr., A159 (1992), 205-221. 

In practice, different types of fatigue testing machines are used for corrosion fatigue experiments, using either traction or bending. The time to failure varies between different experimental arrangements. A direct comparison of test results obtained with non-precracked specimens is possible only if the conditions with respect to all of the discussed variables are the same. 

Figure 5-23. Modeling crack environment for corrosion fatigue in sea water (Turnbull and Ferris, 1987) - comparison with experimental measurements a) crack tip potential, b) crack tip pH.

Figure 2 Corrosion fatigue crack initiation by pitting corrosion (a) Schematic representation of a curve, (b) Comparison of experimentally and theoretically derived fatigue lives for the 20Cr-Ni-Mo alloy in 30 g/L NaCl solutions [8],...

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