Water Corrodes Copper

Abstract

According to a current concept, copper canisters of thickness 0.05 m will be safe for nuclear waste containment for 100,000 years. We show that more than 1 m copper thickness might be required for 100,000 years durability based on water exposures of copper for 20 h, 7 weeks, 15 years, and 333 years. An observed evolution of hydrogen which involves heterogeneous catalysis of molecular hydrogen, first principles simulations, thermodynamic considerations and corrosion product characterization provide further evidence that water corrodes copper resulting in the formation of a copper hydroxide. These findings cast additional doubt on copper for nuclear waste containment and other important applications.

Thermodynamics of H2O Splitting and H2 Formation at the Cu(110)–Water Interface

“…[8][9][10][11][12][13] This would require the formation of a hitherto unknown corrosion product that is more stable than any other phases of the Cu-O-H system. Both computational and experimental efforts have been made to identify and characterize such hypothetical corrosion product, but without success.…”

Physical and chemical properties of Cu(i) compounds with O and/or H

“…For some applications, where the system is driven out of equilibrium, the knowledge of the structure and properties of stable as well as metastable compounds is necessary for for understanding, predicting, and controlling the behavior of copper. Although Cu 2 O and CuOH have been detected as products of copper corrosion under anoxic conditions 4,[6][7][8] , some circumstances of such corrosion behavior are still unclear 9,10 .…”

Scientific basis for corrosion of copper in water and implications for canister lifetimes

“…the thermodynamic stability of copper in the repository environment in the absence of O 2 and HS 2 , has been questioned. [1][2][3][4][5] Figure 2 shows a Pourbaix diagram for the Cu-H 2 O system at 25uC (concentration of dissolved species of 1 mol kg 21 , pressure of gaseous species of 1 atm), for which it is assumed that the only stable copper solids are either Cu, Cu 2 O or CuO. Based on this 'conventional' view of the thermodynamics of Cu in H 2 O, there is 470 mV between the equilibrium potential for the reaction…”

“…(i) copper is oxidised by pure H 2 O with the evolution of H 2 and the rate of anaerobic corrosion of Cu is as high as 5 mm/year 1-5 (ii) corrosion is the result of the formation of a previously unknown phase H x CuO y [3][4][5] (iii) the equilibrium H 2 pressure for the Cu/H x CuO y system is of the order of 1 mbar (101 Pa) at 73uC 3 (iv) a fraction of the hydrogen produced by the reduction of water is absorbed by the copper metal. 4,5 The basic claim that copper is oxidised by H 2 O is based on a number of observations, including (i) the difference in corrosion rate and visual appearance of samples in Pd and Pt sealed vessels 4,7 (ii) ion pump measurements of the flux of H 2 through a Pd membrane 3 (iii) pressure changes owing to the consumption of O 2 and the production of H 2 .…”