Corrosion Fatigue of High Strength Steel in Sea Flowing Water

Jang Soon-Shik, Shoji Tetsuo, Takahashi Hideaki, Watanabe Yutaka

doi:10.3323/jcorr1974.35.9_503

Corrosion fatigue tests were conducted in synthetic sea water to investigate the influence of flow rate on crack growth behavior in various corrosion potentials for HT80 steel. The effect of increasing flow rate under free corrosion potential was to increase the cathodic reaction rate of dissolved oxygen reduction and results in increase of crack propagation rate. When the potential was controlled electrochemically by a potentiostatt at -450mV (vs. Ag/AgCl), it showed different mechanisms with respect to flow rates. At low flow rate, two mechanisms can operate in series with testing time. The first one is hydrogen embrittlement mechanism, which become possible to occur at the crack tip with low pH. After this process, the crack propagation rate decreases with the decrease of effective stress intensity range caused by cumulated corrosion products in crevice after long test period. On the other hand, at high flow rate, the same mechanism as free corrosion potential test governed the crack propagation rate high. In the case of -523mV (vs. Ag/AgCl) test, both low and high flow rates made no difference in crack propagation rate. This result was considered that the impressed current density at low flow rate was high enough to maintain the high crack propagation rate.

Corrosion Fatigue of High Strength Steel in Sea Flowing Water

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