Electrochemical evaluation of crevice corrosion of 430 ferritic stainless steel using the microcapillary tube technique

The aim of this study was to investigate the initiation of crevice corrosion for ferritic 430 stainless steel in artificial crevice electrode cells using the IR drop mechanism. The 430 stainless steel artificial crevice electrodes were potentiodynamically polarized in solutions of sodium chloride with different concentrations. The potentiostatic polarization was measured for various artificial crevice sizes by measuring the potentials in the crevice by the depth profile technique using a microcapillary tube which was inserted into the crevice. The criterion for IR>ΔΦ* , where ΔΦ* is the difference between the applied potential, ESURF, and the electrode potential of the active/passive transition, EA/P, was also measured during the process of crevice corrosion. The potentials in the crevice were successfully measured from −220 mV vs. SCE to −360 mV vs. SCE, which is lower than that of the external surface potential of −200 mV vs. SCE. Thus, these results show that evaluation of corrosion using the IR drop mechanism in the crevice was more objective and easier to reproduce than other existing methods.