Influence of compression fatigue on chloride threshold value for the corrosion of steels in simulated concrete pore

Compression fatigue test was performed on stress level 0.8 for a group of fixed cycle numbers. The steels were soaked in the saturated Ca(OH)2 solution, which was used as simulated concrete pore solution. NaCl was chosen as the sources of chloride ion to corrode the steels. The chloride threshold value (CTV) was detected by combining the open-circuit potential (Ecorr) with corrosion current density (Icorr), which was obtained by electrochemical impedance spectroscopy (EIS). The changes of microstructure that caused by the compression fatigue were observed by optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that the CTV first increased and then decreased with increasing the fatigue cycle times under a certain stress level and range of fatigue life cycles. The grains of the steels became finer and cracks appeared on the protective firms which formed quickly on the surface of the steels. The capacitive arcs under no compression fatigue decreased gradually, while the ones under compression fatigue presented no regularity due to the uneven distribution of the protective films. Cracks on the protective films propagated because of sustaining compression fatigue, which degenerated the later resistances of the steels to chloride ions. Meanwhile, the ranges of corrosion currents were declined.