The corrosion behavior of hafnium in high-temperature-water environments

The high-temperature-water corrosion performance of hafnium is evaluated. Corrosion kinetic data are used to develop correlations that are a function of time and temperature. The evaluation is based on corrosion tests conducted in out-of-pile autoclaves and in out-of-flux locations of the Advanced Test Reactor (ATR) at temperatures ranging from 288 to 360 C. Similar to the corrosion behavior of unalloyed zirconium, the high-temperature-water corrosion response of hafnium exhibits three corrosion regimes: pretransition, posttransition, and spalling. In the pretransition regime, cubic corrosion kinetics are exhibited, whereas in the posttransition regime, linear corrosion kinetics are exhibited. Because of the scatter in the spalling regime data, it is not reasonable to use a best fit of the data to describe spalling regime corrosion. Data also show that neutron irradiation does not alter the corrosion performance of hafnium. Finally, the data illustrate that the corrosion rate of hafnium is significantly less than that of Zircaloy-2 and Zircaloy-4

Erosion-corrosion and wear

The basic processes of wear, erosion and erosion-corrosion are reviewed. It is shown that oxide debris can accelerate wear when it is present as particulates, or protect and reduce friction when it is present as a glaze. Erosion-corrosion processes can be understood and organized in a series of regimes that represent a sequence of change in the relative intensities of erosive and corrosive processes. Types of mechanism expected to feature in oxide spallation and in the erosion-corrosion of alloys are described and, finally, the areas that require serious study in order to achieve further understanding of this subject are indicated