Corrosion behaviour of copper in wet bentonite Rokle B75

Materials for storing nuclear waste are a hot topic all over the globe right now. This study monitors corrosion behaviour of copper as one of the contemplated materials in the Czech bentonite Rokle B75. The tests were carried out in a thermostated cell deaerated with argon at temperatures of 90 and 40°C in the environment of bentonite pore solution, bentonite pore solution with an addition of sulphides and wet bentonite suspension. The scanning electron microscopy, X-ray diffraction, Raman spectroscopy, electrochemical impedance spectroscopy and resistometric methods of corrosion rate measurements were applied. The most compact layer is formed in the environment of bentonite pore solution. The addition of sulphides leads to a significant growth of thickness of the layer of corrosion products and its porosity. However, the porosity decreases towards the layer - metal interface. The layer formed after exposure to the wet bentonite suspension is reported to have the worst parameters. Nevertheless, considering the final temperature of 40°C in the repository, the corrosion rate will still be acceptable.