Characterization of Corrosion Behavior of Irradiated X65 Low Carbon Steel in Aerobic and Unsaturated Gaomiaozi Bentonite

Abstract

2.98 kGy/h (1007 h) gamma irradiation and 90 °C (2000 h) thermal aging were exerted to X65 grade low carbon steel buried in Gaomiaozi bentonite containing 17 wt% Beishan groundwater. The average corrosion rate of X65 low carbon steel was measured. The elemental and phase distribution on cross section was characterized by using electron probe micro-analysis, high-resolution X-ray diffraction, and micro-X-ray diffraction. The following conclusions can be made: the average aerobic corrosion rate of the carbon steel is (45.16 ± 1.53) μm/year. Taking the original surface as boundary, the corrosion scale is divided into an internal dense product layer (DPL) mainly composed of Fe3O4 with segregated FeCO3 at the corrosion front and an external DPL mainly composed of Fe3O4 with segregated α-Fe2O3 and bentonite at some relics. Si, S, and Cl are concentrated at the corrosion front of the internal DPL, while Si and Al are concentrated at the external DPL.