Abstract:Compression fatigue was enforced on Q235 steels with stress level of 08 and different fatigue life cycles. 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 to corrode the steels. The CTV (chloride threshold value) 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 scanning electron microscopy (SEM). The results show that as the fatigue cycle times increases, the CTV increases at first and then decreases under a certain stress level and range of fatigue life cycles. While the capacitive arc under no compression fatigue decreases gradually, the ones under compression fatigue present no regularity.