Effect of dissolved oxygen on corrosion behavior of Zr-0.85Sn-0.16Nb-0.37Fe-0.18Cr alloy in lark 500 °C and 10.3 MPa super-heated steam

To better understand the role of dissolved oxygen (DO) in affecting corrosion behavior of zirconium alloys, the Zr-0.85Sn-0.16Nb-0.37Fe-0.18Cr (wt.%) alloy was corroded in super-heated steam at 500 degrees C and 10.3 MPa under 1 x10(-6) DO and deaeration conditions. The microstructure of the alloy and oxide films was investigated by SEM, 1EM, EDS and EBSD. Results show that the corrosion is aggravated under 1 x10(-6) DO. Compared with the deaeration condition, the oxide film is looser, and has more micro-cracks and more uneven inner surface under DO condition. For the oxide film forming under deaeration condition, the selected area diffraction (SAED) spots of planes (002) m , ((1) over bar 12)(m) and (101)(t) are strong, while those of the (001)(m) and ((2) over bar 12)(m) are weak. However, for the oxide film forming under DO condition, the SAED spots of planes (111)(m), (200) m and (101)(t) are strong, while those of the (100)(m) and (110)(m) are weak. The higher DO content in super-heated steam accelerates the growth of oxide films, thus decreasing the corrosion resistance of zirconium alloys.