Etude électrochimique des mécanismes de la biocorrosion à l'interface de l'acier au carbone en présence de bactéries ferri-réductrices et hydrogénotrophes dans le contexte de stockage des déchets nucléaires.

摘要

The safety of deep geological repository for nuclear waste is a very importantand topical matter especially for the nuclear industry. Such as nuclear fuel the highlevelwaste have to be stored for time frames of millions of years in metalliccontainers. Typically these containers should be placed in deep geological clayformations 500 metres underground. Corrosion processes, will take place after theresaturation of the geological medium and under the prevalent anoxic conditions maylead to the generation of hydrogen. This gas accumulates in clay environmentthrough the years and eventually becomes hazardous for steel containers. In theparticular environment of geological repositories does not provide muchbiodegradable substances. This is the reason that hydrogen represents a newsuitable energy source for hydrogenotrophic bacteria. Thereby formed bacterialbiofilms on the containers may contribute to a process of fast decay of the steel, theso called biocorrosion.The aim of this study is to characterize the electrochemical interfaces in orderto obtain the mechanisms of biocorrosion of carbon steels in presence of ironreducingand hydrogenotrophic bacterium Shewanella oneideinsis.The products of corrosion processes, namely hydrogen and iron (III) oxidesare used as electron donor and acceptor, respectively. The amount of hydrogenconsumed by Shewanella could be estimated with 10-4 mol s-1 using ScanningElectrochemical Microscopy (SECM) techniques.The influence of the local hydrogen generation was evaluated viachronoamperometry. When hydrogen was locally generated above a carbon steelsubstrate an accelerated corrosion process can be observed.Eventually, using Local Electrochemical Impedance Spectroscopy (LEIS)techniques, the mechanism of the generalised corrosion process was demonstrated.