Role of the Oxide Layer in Radiation-Induced Corrosion of Copper in Anoxic Water

The influence of a pregrown copper oxide layer on radiation-induced corrosion of polished copper in pure anoxic water has been explored. The resulting amount of copper oxide formed during corrosion was measured with cathodic reduction, and the concentration of dissolved copper in solution was measured with inductively coupled plasma atomic emission spectroscopy. The identity of corrosion products and their topography was determined with Raman spectroscopy and scanning electron microscopy, respectively. Nonirradiated reference samples were analyzed for comparison. The results show that radiation-induced corrosion of copper in anoxic water is significantly more effective on preoxidized copper compared to polished copper. The total amount of oxidized copper exceeds the amount expected solely from radiation chemistry of water by more than 3 orders of magnitude. To explain this discrepancy a mechanism is suggested where the hydroxyl radical (HO·) is the main radiolytic oxidative species driving the corrosion process. If the thermodynamic driving force would be large enough (such as for the hydroxyl radical or its precursor, H2O+), the oxide layer could conduct electrons from the metal to the hydroxyl radicals formed at oxide surfaces. The formation of an oxide layer will then result in an increased reactive surface area partly accounting for the observed discrepancy.