Microbially influenced corrosion of carbon steel under anaerobic conditions of repository environment containing sulphate reducing bacteria

摘要

Carbon steel is being considered as a candidate canister material for the deep geological repository concept in the Czech Republic. In repositories like this, anaerobic conditions are being expected after the first period in which the oxygen will be consumed. The influence of the microbial activity represents an important part of the safety and performance assessment of a final repository for radioactive waste. The aim of presented work is to characterize the corrosion behaviour of carbon steel in this environment. A corrosion performance was evaluated by means of impedance spectroscopy, resistometric probes, gravimetry, Raman spectroscopy, X-ray diffraction and scanning electron microscopy. Synthetic bentonite pore water mixed with groundwater naturally containing sulphate reducing bacteria represented testing solution. In parallel, the experiment was performed under same conditions without inoculation by microorganisms. The kinetics of anodic and cathodic reaction by means of potentiodynamic curves was evaluated in random composition of synthetic bentonite pore water, according to changes caused by bacteria. The biofilm formation was observed during the experiment in inoculated groundwater. EIS results were used to describe the kinetics and real time interactions between the electrode, biofilm and solution interfaces. Molecular-biological approach was used in order to determine the proliferation of relevant bacterial groups.