Corrosion degradation of infrastructure steel structures in Japan is progressing. At present, maintenance is carried out by observation of the appearance and measurement of the remaining thickness of corroded steel plates. Since technology that enables simulation of remaining ultimate strength has been developed recently, advanced life-time prediction of infrastructure steels, referring even to the corrosion morphology, is now possible. Therefore, in this study, the corrosion form was evaluated by applying spatial statistics to the depth distribution using a laser displacement meter and the effect of Cr content in iron, which significantly varies the corrosion resistance in atmospheric corrosion environments, was quantitatively investigated.

As a result, it was possible to distinguish the corrosion morphology of each Fe-Cr alloys by quantifying the corrosion morphology by range and sill using spatial statistics quantitatively. The diameter of corrosion unevenness increased at 0.3 mass％ Cr alloy. In the case of 1～7 mass％ Cr alloys, the diameter decreased with increasing the content of added Cr. The depth increased with increasing the content of added Cr up to 3 mass％. At 7 mass％ Cr Alloy, the depth was remarkably shallow. Thus, it was proven that the corrosion characteristics of the base metal greatly influence the corrosion morphology of Fe-Cr alloys.