加工誘起マルテンサイト相を含むSUS 304鋼の水素吸収による耐食性劣化の機構

抄録

The mechanism of the degradation of corrosion for deformed Type 304 steel exposed to 28 MPa hydrogen at 673 K for 57.6 ks has been investigated by electrochemical measurements. The anodic polarization curve of hydrogen-charged martensitic Type 304 steel in H₂SO₄ solution shows three anodic peaks at the potentials of −0.4, −0.3 and −0.05 V vs. SCE, whereas that of hydrogen-charged austenitic steel does the peaks at −0.3 and −0.05 V vs. SCE, but not the peak at −0.4 V vs. SCE. Severe corrosion was observed on the hydrogen-charged martensitic steel when it was held at −0.4 V vs. SCE in H₂SO₄ solution. This severe corrosion was prevented by heating the steel at 923 K, although it was not avoided up to 873 K. It was found that the cathodically hydrogen-charging at ambient temperature induced martensite phases in the austenitic steel, and it did a hydride phase at 373 K. The anodic polarization curve of Type 304 steel containing a hydride phase revealed an anodic peak at −0.5 V vs. SCE, while that of the steel containing hydrogen-induced martensite phase did not produce the peak at −0.4 V vs. SCE. Consequently, the degradation of corrosion of deformed and hydrogen absorbed Type 304 steel can be ascribed to the selective corrosion of hydride in martensite phases by deformation.