Analysis of the polarization current responded to cyclic strain during corrosion fatigue of iron

Corrosion fatigue tests of a commercial iron were carried out in a borate buffer solution containing sodium chloride at a constant passive potential. In order to detect crack initiation and quantify the extent of corrosion fatigue damage, the polarization current responding to the strain cycles has been studied. From this current, the current amplitude and the phase shift between the current and the strain were calculated. By analysis of these parameters, crack initiation was detected in such an early stage of about 10% of the fatigue life. The extent of the surface damage was detected from the distortion of the wave form due to the higher harmonics components. The corrosion fatigue process was investigated by the polarization current behavior.