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

Abstract

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.

Corrosion of carbon steel and the passivating properties of corrosion films formed under high-PT geothermal conditions

“…For instance, it was found that Fe-reducing bacteria can substantially enhance corrosion rates by destabilizing magnetite at temperatures below 100°C (Schütz et al, 2015;Spark et al, 2017). Mixed cation/anion solutions, like most natural waters, might also lead to a different outcome with respect to corrosion and particularly to film formation (Lee et al, 2006).In NWD, γ radiation originating from the spent nuclear fuel may produce powerful oxidants by radiolysis (HO•cm) aq, H2O2) that enhance metal corrosion substantially (Björkbacka et al, 2016).…”

The Effects of Cathodic Reagent Concentration and Small Solution Volumes on the Corrosion of Copper in Dilute Nitric Acid Solutions

“…The peaks at 525 cm −1 , 625 cm −1 , 147 cm −1 , and the faint peak at 220 cm −1 indicate the presence of Cu 2 O. [20][21][22][23][36][37][38][39] The detection of this phase in the absence of any discrete deposited crystals suggests Cu 2 O is present as a pervasive surface film. Given the roughness of the corroded surface, it is possible these Raman responses are surface-enhanced 29 and that the variations in peak intensities reflect the different corrosion rates on different crystal faces, with strong signals surface enhanced.…”

“…At higher dose rates (80 Gy/h to 770 Gy/h), more extensive corrosion was observed with the deposited corrosion product film (predominantly Cu 2 O) thought to play a significant role in amplifying the influence of ϒ-radiation. 23 Under unsaturated aerated conditions more relevant to these studies, modest dose rates (100 Gy/h [90°C to 150°C]) 24 also lead to the formation of an apparently protective Cu 2 O layer, the corrosion rate being only marginally greater (∼1.5 times) than that in the absence of radiation. At a higher dose rate (700 Gy/h), cupric nitrate (Cu 2 NO 3 (OH) 3 ) was formed, again suggesting the establishment of oxidizing surface redox conditions sufficient to cause oxidative breakdown of the Cu 2 O base layer and the incorporation of radiolytically-generated NO − 3 into the corrosion product.…”

“…Under these conditions the radiolysis of the aerated vapor will produce HNO 3 , 10-12 which will be absorbed into condensed H 2 O in contact with the aerated vapor. [13][14][15] The effect of radiation on the corrosion of Cu has been studied in both aqueous solutions [16][17][18][19][20][21][22][23] and in humid air, 24 usually at dose rates well in excess of those anticipated on a container surface, but with contrasting observations. In both aerated and deaerated chloride solutions (150°C, 27 Gy/h), radiation appeared to be beneficial, leading to the formation of an apparently protective Cu 2 O film.…”

Exposure tests of copper foils in a slurries of different bentonites

“…Copper is material believed as corrosion resistant in wet bentonite environment of radioactive waste deep geological repositories. It is candidate material for outer case in Scandinavian concept [1][2][3][4][5] and for coating in Canadian [6][7][8][9][10]. Copper is also one of the candidate materials for construction of canisters in Czech concept [11][12][13][14][15][16][17][18].…”