Preliminary electrochemical corrosion monitoring of iron in mixture cement paste–bentonite

ABSTRACTIn the context of the French 500-m deep radioactive waste repository, electrochemical impedance spectroscopy and a methodology based on complex impedance analysis were carried out to follow the hydration of grout containing cement–bentonite mixture and iron corrosion together. The grout was initially a paste, and solidified with time. After a 100-day-curing, the temperature of the system (grout + steel) was increased from room temperature to 80°C to simulate the effect of a nuclear waste overpack. At room temperature, the ionic conductance exhibited a continuous decrease followed by an increase at 80°C. After an initial drop, the corrosion rate increased to a quasi-steady state value at around 1.5 µm/year at 21°C. At 80°C, the corrosion rate increased to about 30 µm/year before gradually dropping to much lower values. Eventually, then the passivation of iron seemed to occur since the corrosion rate has decreased continuously down to 0.1 µm/year.This paper is part of a supplement on the 6th Interna...