Corrosion behavior of Zr?Nb alloys in 360°C water and 500°C supercritical water

The corrosion behavior of Zr−0.4 wt.%Nb and Zr−1.5 wt.%Nb alloys was investigated in 360°C water and 500°C supercritical water. The two Zr−Nb alloys showed a similar corrosion rate in both corrosion conditions. However, in the 500°C supercritical water, the corrosion rate was increased by 23 times when compared to that of the 360°C water based on the weight gain at 240 days. In terms of the relationship between the corrosion and the precipitate characteristic, the β−Nb precipitates in the Zr−Nb alloys were considered to play an important role in the excellent corrosion resistance in the 360°C water, but its beneficial effect was not maintained in the 500°C supercritical water. The oxide characterization revealed that the tetragonal phase stability was more easily decreased from the interface to the surface in the oxide formed in the 500°C supercritical water.