Rapid determination of corrosion under fatigue loading based on tensile loading

This study tests the hypothesis that corrosion properties under fatigue loading can be evaluated based on simple tensile tests without the need to perform costly and time-consuming corrosion fatigue tests. Two types of stainless steel 304L specimens, i.e., smooth and compact tension (CT), are exposed to static and fatigue loading in two aqueous solutions with different NaCl concentrations. Strain analysis, surface roughness measurements, scanning electrochemical microscopy (SECM), and Tafel polarization techniques are employed to unveil the effects of mechanical stress and strain on the corrosion behavior at micro and macro scales, a phenomenon known as electro-chemo-mechanical interaction. Finite element analysis (FEA) is performed to calculate the stress and strain field in the specimens. Digital image correlation (DIC) is used to validate the FEA results. The results indicate a strong correlation between the static stress, strain, and surface roughness with the corrosion rate. In particular, the study reveals a strong correlation between corrosion current (and corrosion current density) under fatigue loading with that under static tensile loading, thereby providing a means to evaluate the corrosion properties under fatigue loading solely from static tests. Fatigue loading leads to a progressive reduction in the corrosion potential as the number of cycles increases. The corrosion current density, icorr, is linked to the stress and accumulated plastic strain through by an empirical equation, shedding lights on the complex electro-chemo-mechanical interaction. Additionally, opportunities for future research are discussed.