抄録
Critical potentials for pitting (Epit) and crevicice corrosion (Ecrev) for type 304 stainless steel have been determined from long-term steady polarization tests in deaerated NaCl solutions as a function of NaCl concentration at 423K. Epit and Ecrev were expressed by the conventional form: E=A-B log[Cl-], where A and B in volt vs. SHE were -0.19 and 0.15 for Epit and -0.20 and 0.10 for Ecrev, respectively. The comparison of Epit with pitting potential (E′pit) and repassivation potential (ER, pit), which were repeatedly determined from stepwise cyclic polarization tests, showed that ER, pit distributed less nobly than Epit especially at lower NaCl concentrations and that Epit could be described as a lower limit of Weibull's distribution function for E′pit. The similar analysis for crevice corrosion showed that the noblest value of ER, crev for its dependency on corrosion extent corresponded to Ecrev but the distribution in E′crev at different concentrations of NaCl could not be described by the Weibull's function with an identical shape parameter.
