We have studied copper corrosion in a system comprised of deionized water, absolute pressure gauges, and a palladium membrane. A transition from O 2-consuming to H 2-evolving copper corrosion is observed, which indicates that copper can corrode by water itself. The equilibrium hydrogen pressure in corrosion of copper by water at 73°C exceeds the steady-state atmospheric hydrogen pressure ͑5 ϫ 10 −7 bar͒ by a factor of about 2000. The growth of a hydrogen-containing corrosion product in O 2-free water is controlled by the hydrogen removal from the corroding surface. The results are discussed in the perspective of conventional potential-pH diagram for copper.
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.
The oxide films formed on AISI 316L͑NG͒ in the temperature range 150-300°C have been characterized by impedance spectroscopy and ex situ analysis using Auger electron spectroscopy. Relatively thick films containing a high concentration of mobile defects form on stainless steel in a high-temperature borate electrolyte, but their impedance response is most probably controlled by the properties of a thin barrier sublayer. The ability of the mixed conduction model for passive films to reproduce the experimental impedance data in both alloy/oxide/electrolyte and alloy/oxide/inert metal configurations has been tested. A procedure for the calculation of the kinetic constants of the interfacial reactions of point defect generation/consumption, as well as those characterizing the transport rates of ionic/electronic defects in the oxide, has been developed. The effect of temperature on the kinetic and transport parameters has been assessed, and the relevance of these parameters for the corrosion behavior of stainless steel in a high-temperature electrolyte is discussed. The results show that the nature of the barrier layer does not change drastically with temperature, although the growth mechanism of the oxide film is different at 150-300°C than at room temperature.The materials used in contact with the coolant in nuclear power plants rely almost exclusively on a passivating oxide film to ensure durability and structural integrity. A slow and well-controlled growth of the passive film is necessary in order to limit the impact of the coolant on these materials and to minimize the concentration of impurities that may reach the nuclear fuel surfaces and thus become radioactive.The development of knowledge of the oxide film composition and behavior, as well as the knowledge of the local coolant chemistries, has converged considerably during the last few years. 1,2 It is hence known that the oxide films formed on stainless steels and nickel-based alloys in high-temperature water have basically the same main structure and that the important compounds ensuring the protective character of the oxide film ͑nickel ferrite and nickel and iron chromites͒ are essentially the same for all the nickel-based materials and stainless steels. [3][4][5][6][7][8][9][10][11][12][13][14][15] In addition to the increased understanding of growth and restructuring of oxide films, recent development of radiolysis codes allows the modeling of the chemistry resulting from the radiolysis in virtually any location where the coolant is in contact with any material in light water reactors. The modeling provides the concentration of all radiolysis products, including radicals, and also calculates the local electrochemical corrosion potential in each location, hence providing the basis for determining or establishing thermodynamic, kinetic, and electrokinetic phenomena. 16 We hence have the qualitative understanding of most of the important processes during film growth and restructuring, with their background and implications. 17,18 What we still lack today i...
The second-phase particles (SPP) play an important role on the corrosion and hydriding properties of BWR Zircaloy-type materials. It has been proposed that the chemical composition of the SPPs as well as the SPP size distribution strongly affect the in-reactor performance. Zr-Fe, Zr-Cr, and Zr-Ni binary alloys were processed, the size and density of SPP being independently varied through chemical composition and heat treatments. SEM imaging was used to measure the grain size and the SPP size and distribution. Significant differences between binary alloys with iron, chromium, and nickel were observed. Grain sizes depend primarily on size and volume fraction (VF) of SPP. The SPP kinetic growth varies with the alloying element. These observations are compared with corrosion and hydriding data obtained from autoclave experiments at 415 and 500°C, which show that besides the SPP size, their volume fraction is an important parameter (increasing the volume fraction decreases the corrosion rate, whatever the nature of the SPP). On the contrary, air oxidation at 415°C shows very slight influence of SPP type, size, and volume fraction on the corrosion resistance of the material. It should, however, be noticed that the considered test was a short-term test (3 days) and that the oxide layer thickness was less than or around 1 μm for all tested materials. Electrochemical impedance spectroscopy as well as potential sweep and step experiments were used to study the oxidation properties of the binary alloys at room temperature. On samples with large particles, thin compact oxide films are formed. In contrast, on samples with many small particles thick porous oxides are formed. Based on these results and the SPP volume fraction, a tentative mechanism of corrosion and hydriding is proposed, explaining the differences in uniform and nodular corrosion observed between different Zr-based alloys.
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