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Electrochemical behaviour of non-alloy steel reinforcement in alkaline solutions


For many countries, and taking into account the safety assessment, it is expected that high-level nuclear wastes (HLW) will be confined in deep underground repositories. For that purpose, a very thorough study was planned in order to guarantee, in first place a presence of artificial and geological barriers surrounding waste and in second, a long life and a strong resistance to corrosion of the formwork. The French concept plans to embed HLW in a glass matrix cooled in a stainless steel container (primary package). This package will be emplaced in a low-alloyed carbon steel over pack prior to being inserted in the casing, which will be inside a disposal cell, i.e. a tunnel drilled within the host rock. The over pack aims at preventing water from reaching the vitrified waste during the thermal phase (temperature T ≥ 50◦C), while the casing (also made of C-steel) has a mechanical function, as it should allow the nuclear waste to be recovered forover a century. The Callovo-Oxfordian (COx) claystone has been selected as the potential host rock for this HLW, because of its good confinement properties and low water permeability. Once the repository is closed, O2 will be consumed rapidly and anoxic conditions will prevail afterwards [1]. In this work, the electrochemical behaviour of two steels grades was studied in different simulated concrete pore solutions simulating the alkaline environment of reinforcing steel rebars at 25°C. For that purpose, electrochemical measurements were performed at Ecorr or under anodic polarization in order to determine the corrosion current density of the system. These experiments were performed under anoxic conditions or in the presence of oxygen but also with or without the addition of dry concrete in the electrolyte. Under anoxic condition and without adding dry concrete, a steady state is reached after 14h of immersion and a passive layer is then formed at the steel surface. The estimation of the oxide layer thickness using the Cole-Cole approach [1] confirms the presence of an oxide protective layer at the steel surface with a thickness of about 2 nm. The passive current density is then equal to 40 nA.cm-2. The addition of the dry concrete in the solution induces a decrease of pH solution. As consequence, the oxide layer formed at the steel surface is no more protective. In aerated solution, with or without adding dry concrete, the corrosion potential drops after several hours of immersion inducing the corrosion of the electrode surface. [1] M. Benoit, C. Bataillon, B. Gwinner, F. Miserque, M. E. Orazem, C. M. Sanchez-Sanchez, B. Tribollet, V. Vivier, Comparison of different methods for measuring the passive film thickness on metals, Electrochim. Acta 201 (2016) 340.
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hal-03976345 , version 1 (07-02-2023)


  • HAL Id : hal-03976345 , version 1


Sara Chakri, Eliane M M Sutter, Mai T.T. Tran, S. Necib, D. Crusset. Electrochemical behaviour of non-alloy steel reinforcement in alkaline solutions. EuroCorr 2017, Sep 2017, Prague, Czech Republic. ⟨hal-03976345⟩
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