Susceptibility of Zr-2.5 (wt. %) Nb alloy to undergo nodular corrosion in water and steam environments: Effect of surface, cold work, temperature

Nodular corrosion can severely affect the service life of zirconium alloys in water cooled nuclear reactors. In this study, the susceptibility of pressure tube alloy to undergo nodular corrosion in water-steam with air surroundings at 250°C and 300°C is investigated. Accelerated corrosion has been studied in single phase steam at 500°C. The effect of specimen surface condition and cold work on nodular corrosion susceptibility has been studied in detail. The results indicate that surface condition of the specimen plays primary role in determining the propensity of the alloy to undergo nodular corrosion. Cold work has negligible effect on the initiation as well as growth of oxide nodules in Zr-2.5 (wt. %)Nb alloy. The effect of temperature is highly localized and is visible on the size of the nodules. Presence of non-uniform or discontinuous autoclave layer increases the susceptibility of pressure tube alloy to undergo nodular corrosion.