Corrosion behavior and oxide microstructure of Zr-1Nb-xGe alloys corroded in 360 °C/18.6 MPa deionized water

•Corrosion resistance of zirconium alloys is improved by Ge addition.•Corrosion resistance is optimal when Ge contents is 0.05%.•Ge retards the evolution from columnar grains to equiaxed grains.•Ge delays the developing process of defects to form micro-cracks in oxide.•The sub-oxide layer identified as cubic-ZrO was detected at oxide/metal interface.

The corrosion behavior and microstructures of the oxide film on Zr-1Nb-xGe alloys (x = 0, 0.05, 0.1 and 0.2, wt%) corroded in deionized water at 360 °C/18.6 MPa were investigated. Results showed that the Zr-1Nb-0.05Ge alloy possessed much better corrosion resistance than the Zr-1Nb alloy. The Ge dissolved in the α-Zr matrix can retard the microstructural transformation of ZrO2 from the columnar grains to equiaxed grains and delay the process of the defects developing into micro-cracks in the oxide. The amorphous phase produced around the [Zr–Nb–Fe–Cr–O] SPPs can improve the corrosion resistance by relaxing the compressive stress in the oxide films. The sub-oxide layer identified to be cubic-ZrO may improve the corrosion resistance after corrosion transition.