Corrosion of Zircaloys: Relating the microstructural observations to the corrosion kinetics

Understanding the corrosion behaviour of zirconium alloys is essential in providing cost effective and safe operation of nuclear power plant. Long-term corrosion testing of Zircaloy-4 and Zircaloy-2 in 350 °C pressurised water is presented with detailed analysis of the oxide's development. The correlation of the corrosion and analytical data provides a detailed understanding regarding the point at which different microstructural features, such as cracking, occur during the cyclic corrosion process. The results from this work show that the large scale cracking, which is often associated with the cyclic transitions, evolve following, rather than prior to, the onset in rapid corrosion.