SUS 304鋼の表面近傍深さ方向Cr濃度分布の電気化学的測定法

抄録

The depth-profile of Cr concentration of Cr depleted zone formed under oxide film of stainless steels during oxidation process plays an important role in the corrosion behavior and oxidation resistance. In order to produce stainless steels with high quality surface, speedy and exact measurement of the depth-profile of Cr is required, through which production process should be properly controlled. In this paper, a new method is presented for measurement of the depth-profile of Cr. This method depends on the relation between the Cr concentration of stainless steel and the current density in transpassive region in H₃PO₄ solution at 323K. SUS 304 steel which was oxidized in air at 1, 273 K, and then removed oxide film by mechanical polishing, was polarized at +1.40 V (SCE) (transpassive region) in 10% H₃PO₄ (air open, 323K) in order to measure the i_{t, p} (10^-3A·cm^-2)-Q (C·cm^-2) curve. From the i_{t, p}-Q curve, the depth-profile of Cr was obtained by converting i_{t, p} into Cr concentration and Q into depth. The usefulness of this method was evaluated through the comparison between the depth-profile of Cr measured by this method and the one calculated and measured by evaporation model, AES, EPMA, chemical analysis respectively.