Anomalous Corrosion of Austenitic Stainless Steel Exposed to Hydrogen at High Temperature and Pressure

The effect of dissolved hydrogen on intergranular and general corrosion of austenitic stainless steels was investigated. Hydrogenation was carried out in 1 to 28 MPa hydrogen at 723 K for 16 hours. The corrosion rate of hydrogenated AISI 304 stainless steel, with precipitated carbides in grain boundaries or contained martensites, was markedly greater than that of hydrogen-free ones. This anomalous corrosion increased with the hydrogen content of steel. The current density of the anodic polarization curves of hydrogenated specimens was greater than that of hydrogen-free ones, which coincided with the corrosion data. This anomalous corrosion recovered with the short time heating at 923 K and above, but not with the heating at 873 K and below. These behaviors can be interpreted by the formation of internal microdefects, which are active sites, and impair the passivation characteristics, caused by hydrogen trapping.