6th International Workshop on Long-term Prediction of Corrosion Damage in Nuclear Waste Systems
Toronto, Ontario, Canada, May 9-12, 2016
Corrosion of Mg and Mg alloys in a Na-geopolymer and in its synthetic poral solution
B. E. Torres-Bautista1, J. Agullo2, B. Muzeau1, C. Bataillon2
1
2
CEA, DEN, DANS, DPC, SECR, Laboratoire d’Etude du Comportement des Bétons et des
Argiles, F-91191 Gif-sur-Yvette, France
CEA, DEN, DANS, DPC, SCCME, Laboratoire d’Etude de la Corrosion Aqueuse, F-91191
Gif-sur-Yvette, France
ABSTRACT
The reprocessing of spent fuels from UNGG (Uranium Natural Graphite Gas) nuclear reactors in
France has generated cladding wastes mainly made of Mg alloys [1]. The waste will be
conditioned in a waste-package, ensuring durability, handling capability, and confinement of the
radionuclides during further storage period and final disposal (mainly during the operational
phase) [2]. The use of geopolymers is currently studied at CEA as new binders for the
conditioning of these metallic wastes [1] [3]. The alumino-silicate matrix considered here is
activated with NaOH in the presence of sodium fluoride (Na-Geo/NaF), fluoride ion being a
corrosion inhibitor for Mg and its alloys [4].
Moreover, the Mg cladding wastes could be in direct contact with residual graphite materials,
initially present in the fuel assemblies or steel from the container, leading to a potential galvanic
corrosion. With a standard potential of -2.36 V / NHE, Mg and its alloys acts as anode in most
galvanic corrosion processes, this results in the acceleration of the corrosion rate of Mg and the
significant hydrogen evolution [5] [6].
The aim of this work was to study the general and the galvanic corrosion behaviour of Mg and
Mg alloys either in Na-Geo/NaF geopolymer or in its synthetic poral solution. To ensure such
study, electrochemical methods (Ecorr vs time, ZRA, polarization curves and EIS), weight loss
measurements and surface analysis were used.
Corrosion rates of pure Mg, Mg-0.5%Zr and Mg-0.5%Zr/Aguadag® were estimated by EIS and
polarization curves after 24 h of immersion in a synthetic poral solution. EIS results were
analyzed by using a methodology based on complex impedance analysis [4]. On the other hand,
general corrosion of pure Mg and Mg-1.2% Mn and galvanic corrosion of Mg-1.2% Mn/Steel
S235JR and Mg-1.2% Mn/Aquadag® were studied by weight loss measurements. Coupons were
embedded in Na-Geo/NaF geopolymer or immersed in its synthetic poral solution during 180
days. First results, after 28 days, show that the average corrosion rates determined are of several
tens of μm.year-1 corresponding to hydrogen production between 0.1-0.2 L.m-2.day-1.
References
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6th International Workshop on Long-term Prediction of Corrosion Damage in Nuclear Waste Systems
Toronto, Ontario, Canada, May 9-12, 2016
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