In order to reduce the weight of the suspension springs by increasing the strength level of the steels used, it is necessary that the corrosion fatigue property should be improved. However, the dominant factor governing the corrosion fatigue property of the suspension spring has not been satisfactorily revealed yet. Therefore, the investigation into elucidating the mechanism has been carried out to evaluate the effects of corrosion pits, shot peening, hydrogen embrittlement, prior-austenite grain size, and so forth independently on the corrosion fatigue property. In this work, focus was placed upon the effects of corrosion pit depth and shot peening on the fatigue property. The specimens having the different artificial corrosion pits depth were subjected to fatigue tests. Special attention was paid to exclude the influence of hydrogen. As a result, it was revealed that the fatigue limit decreased with the increase of the corrosion pit depth, presumably due to the decrease in the compressive residual stress at the bottom of corrosion pit. Moreover, the effect of prior-austenite grain size on fatigue properties turned out to be almost negligible.
