Abstract
The corrosion fatigue tests of mild steel have been carried out under various mean stresses, and electrochemical discussions have been made on the progress of corrosion fatigue damage with corrosion potential, corrosion current and polarization characteristics.
The corrosion potential under static stresses remarkably shifts to the anodic, irrespective of tension or compression, when the applied stress exceeds the elastic limit, and the deformation becomes plastic. In corrosion fatigue, the mean tensile stresses accelerate the increase of fatigue damage, which is found to be caused by the greater increase of the slope of anodic Tafel lines. On the contrary, the mean compressive stresses suppress the increase of its fatigue damage when the work hardening by the repetitive stresses has been completed, which is found to be caused by the smaller increase of the slope of anodic Tafel lines and by the delay of fatigue crack propagation.
Under the catholic protection of corrosion fatigue, the incubation period before the occurrence of iron dissolution is found longer under the mean compressive stresses than under the mean tensile stresses, which suggests the easier applicability of the cathodic protection under the mean compressive stresses.
