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Databank

Posiva publishes Working Reports and Posiva Reports. From the year 2006 nearly all the reports have been published on our webpage and they can be found in the databank. In the databank you can also find our Annual Reviews and some other publications as well. You can also find print-quality pictures and useful links in the databank.

Recent publications


Workreport 2018-19

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Name:

Copper Corrosion Experiments in Pure Water Under Anoxic Conditions

Writer:

Ollila, K.

Language:

English

Page count:

60

Summary:

This report gives the results of the corrosion experiments with copper, which were conducted in pure water under anoxic conditions. Copper is generally assumed to be rather immune under these conditions. Some results from literature suggest a corrosion reaction to occur by water forming hydrogen.

The corrosion experiments of the first part of this report imitated the experimental methods used by Hultquist et al. (2009). The experiments with Cu strips (OFHC, 99.95 % Cu) were conducted in degassed deionized water in sealed Erlenmeyer flasks in the glove box (N2, Ar). This work includes the termination and the analyses of the Cu4 experiment after 6.8 years’ duration. The Cu4 E-flask had palladium foil as hydrogen permeable closure. At the end of the experiment, there were no visible changes on the surfaces of the Cu strips, similarly with its parallel experiment Cu3, which was finished after 2 years’ duration (Ollila 2013). Hydrogen was observed in the empty phase of the E-flask and in the Pd foil. The measured weight losses showed that both of the E-flasks, Cu3 and Cu4, had not remained completely tight during the long experimental periods, which makes it difficult to draw any conclusions from the H2 analyses. A layer of Cu(I)-oxide, Cu2O, was indicated by XPS-analyses on the surface of Cu4 strip at the end of the corrosion experiment. No Cu(II) was observed. Cu2O was observed also on the surface of the reference sample suggesting the polishing prior to the start of the experiments was not able to remove all oxidized layer.

A new set of corrosion experiments were conducted in degassed ultrapure water in Bellco vials and bottles with gas impermeable septum closures. A comparable method was used by Bengtsson et al. (2013). The septum closure enables gas sampling with an injection needle through the butyl rubber stopper. The copper qualities were phosphorous OFP-Cu (99.99 % Cu, 50 ppm P) and pure 6N-Cu (99.9999 % Cu). The aim was especially to find out hydrogen observations in the experiments. The copper rods were polished mechanically and chemically using a multistage method to remove oxidized layers from surfaces. The durations of the experiments varied between 1 week and 6.5 months. The analysed hydrogen concentrations in the empty volumes of the test vials suggest difference between the copper types. The H2 concentration increased in the gas phase with the duration of the test with OFP-Cu, while it remained at the level of the blank tests with 6N-Cu. In order to evaluate if the observed hydrogen could be released from the copper material during the test periods, the H2 concentrations of the rods were analysed before and after the experiments. The hydrogen concentrations of OFP-Cu rods showed a slowly decreasing trend with longer durations. This was complicated by the variation in the results of H2 analyses between the specimens from one rod and between the rods. The XPS results do not suggest any corrosion reactions the Cu surface to have occurred in the experiments. The dominant chemical state of Cu on the surface of the analysed Cu rods was metallic Cu(0) at the end of the test periods. The presence of oxidixed layers, Cu2O, Cu(OH)2 or CuO, was not observed by XPS on the exposed copper surfaces. Cu2O was observed on the surface of the reference sample suggesting the initial careful polishing and chemical treatment was not completely efficient to remove the oxidized layer, but it seems to dissolve during the experiments.

Keywords:

Copper, corrosion, corrosion of disposal canister, corrosion of copper, corrosion in pure water, corrosion under anoxic conditions

File(s):

WR 2018-19_web (pdf) (9.2 MB)


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