Effect of Vacuum Annealing on the Compositions of U-0.79wt% Ti Alloy Surface Exposed in a Salt Fog Environment

The evolution of the compositions in two typical regions on U-0.79wt% Ti alloy surface exposed in a salt fog environment was investigated by x-ray photoelectron spectroscopy (XPS) during vacuum annealing. The results show that pitting corrosion tends to occur around titanium inclusions on the alloy surface in the environment containing chloride ions. The compositions in the two regions were transformed with experimental temperature increasing. The complex oxide compound, alpha-U3O8, was detected by both XPS and Raman spectrum in the blackened region, while UO2 vertical bar x/UO2 were the main oxide compounds in the other region where pitting corrosion did not occur. The different compositions in the two typical regions were slightly changed as temperature ramps up from room condition to 200 degrees C. The alpha-U3O8 in the blackened region started to be reduced to UO2 while UO2+x in the other region to be converted into UO2 at 300 degrees C. An oxycarbide (UOxCy) compound was observed due to the reaction between UO2 and carbon at 400 degrees C. Between 500 degrees C and 700 degrees C, the UOxCy formed in the blackened region was partly converted into UO2, while the UOxCy formed in the other region was almost completely converted into UO2, which was in turn reduced to metallic uranium.