On corrosion of zirconium alloy in dissolved oxygen water: The role of Cu addition

It is significantly important to improve the corrosion resistance of Zr-Sn-Nb alloys in dissolved oxygen (DO) high temperature water by compositional modification. Here, the effect of Cu addition on the corrosion behaviors of Zr-0.5Sn-0.2Nb-0.4Fe-0.2Cr alloy was studied by using an autoclave circulating water loop at 360 degrees C/20 MPa up to 250 days. The oxide microstructures were characterized by a combination of SEM, TEM, STEM-EELS and PED. The results showed that compared with 0Cu alloy and 0.07Cu alloy, 0.13Cu alloy shows better corrosion resistance and its final weight gain after 250 days exposure is even lower than that of commercial Zr-4 alloy. The oxides for 0.07Cu and 0.13Cu alloys show more ordered crystals, thinner oxide and less lateral cracks, and the columnar grains show a stronger {10-3} texture, compared to Cu-free counterpart. The t-Zr2Cu SPPs have oxidized in the oxygen-rich layer below the O/M interface. The Cu ions tend to diffuse towards the grain boundary of dense columnar grains and maybe strengthen the grain boundaries, avoiding the defect generation under intrinsic stress in the oxide.