定電位CERT法によるSUS304オーステナイトステンレス鋼の3%NaCl溶液における応力腐食割れに関する金属電気化学的研究

Abstract

The SCC of the Type 304 austenitic stainless steel in 3%NaCl solution (293 K) was studied by the potentiostatic CERT method in conjunction with its polarization behavior. The mechanical properties and the current flowing through the specimen were measured by the potentiostatic CERT method in the range of crosshead sbeed from 1.67×10−7 m/s to 1.67×10−5 m/s, and the fracture surface was examined by a scanning electron microscope. From the polarization behavior of the Type 304 stainless steel in 3%NaCl solution at 293 K, it was found that the specimen was very susceptible to the SCC in the pitting potential (0.34 V vs NHE), and was immune to the SCC both in the steady passive potential (−0.06 V vs NHE) and the unsteady one (1.14 V vs NHE).The tensile strength and the reduction of sectional area in the pitting potential decreased remarkably at the low crosshead speeds below 1.67×10−6 m/s, and this was most likely due to the SCC caused from the pitting corrosion.