Effect of isothermal annealing on the corrosion behavior of Zr–xNb alloys

To study the effect of isothermal annealing on the corrosion behavior of Zr–xNb alloys, several systematic studies on corrosion and oxide characteristics were performed for the Zr–xNb alloys (x=0.1∼2.0 wt%). The samples were annealed at 570 °C for 0–1000 h after β-quenching. The corrosion resistance of the 0.1 and 0.2 wt% Nb alloys where Nb existed in the equilibrium soluble state in the matrix was excellent in the quenched and annealed conditions. For the high Nb-containing alloys, the corrosion rates were very sensitive to the annealing condition, and it took about 50 h at 570 °C to reach corrosion rates comparable to the low Nb wt% alloys. The corrosion resistance is correlated to the stabilization of the tetragonal ZrO2 and columnar oxide structure when the Nb concentration in the matrix is reduced to the equilibrium soluble limit.