Abstract
The MCO experiment was carried out over a period of 12 years in the Underground Research Laboratory (URL) of Andra to investigate long-term effects of iron-claystone interactions. The test chamber consisted of two cylinders: the external cylinder (EC) was made up of Callovo-Oxfordian claystone (COx); the internal cylinder (IC) was a mixture of crushed COx and iron grains. A central heater system and water seepage simulated the heat released by the radioactive decay and the circulation of clay porewater respectively. A multi-technique characterization indicates that the EC showed very little changes in comparison with the pristine claystone. The clay particles of IC become enriched in Fe3+ and evolve towards a composition close to odinite/berthierine. Several corrosion products are identified but no magnetite is observed, although this mineral is thought to be at the origin of the passivation effect playing a role in the corrosion rate and porosity clogging. The released iron remains in the IC and migrates up to the interface between the two cylinders. This underlines that the effect of iron corrosion on the surrounding host-rock is restrained to a small portion of COx, whereas the rest of the rock preserve its properties suitable for a HLW repository.
Similar content being viewed by others
Data availability
The data related to the findings of this study are available within the paper on in Supplementary material, and any other supporting data could be provided by the corresponding author on reasonable request.
References
Perronnet, M. et al. Towards a link between the energetic heterogeneities of the edge faces of smectites and their stability in the context of metallic corrosion. Geochim. Cosmochim. Acta 71, 1463–1479 (2007).
Mosser-Ruck, R. et al. Effects of temperature, pH, and iron/clay and liquid/clay ratios on experimental conversion of dioctahedral smectite to berthierine, chlorite, vermiculite, or saponite. Clays Clay Mine 58, 280–291 (2010).
Jodin-Caumon, M. C. et al. Mineralogical evolution of a claystone after reaction with iron under thermal gradient. Clays Clay Min. 60, 443–455 (2012).
Gaudin, A. et al. First corrosion stages in Tournemire claystone/steel interaction: in situ experiment and modelling approach. Appl. Clay Sci. 83, 457–468 (2013).
Bourdelle, F. et al. Iron–clay interactions under hydrothermal conditions: impact of specific surface area of metallic iron on reaction pathway. Chem. Geol. 381, 194–205 (2014).
Pignatelli, I. et al. Iron–clay interactions: detailed study of the mineralogical transformation of claystone with emphasis on the formation of iron-rich T–O phyllosilicates in a step-by-step cooling experiment from 90 C to 40 C. Chem. Geol. 387, 1–11 (2014).
Rivard, C. et al. Reactivity of Callovo-Oxfordian claystone and its clay fraction with metallic iron: role of non-clay minerals in the interaction mechanism. Clays Clay Min. 63, 290–310 (2015).
Ngo, V. V., Clément, A., Michau, N. & Fritz, B. Kinetic modeling of interactions between iron, clay and water: comparison with data from batch experiments. Appl. Geochem. 53, 13–26 (2015).
Mosser-Ruck, R. et al. Serpentinization and H2 production during an iron-clay interaction experiment at 90°C under low CO2 pressure. Appl. Clay Sci. 191, 105609 (2020).
Necib, S. et al. Corrosion at the carbon steel-clay borehole water and gas interfaces at 85° C under anoxic and transient acidic conditions. Corros. Sci. 111, 242–258 (2016).
Bildstein, O., Trotignon, L., Perronnet, M. & Jullien, M. Modelling iron-clay interactions in deep geological disposal conditions. Phys. Chem. Earth 31, 618–625 (2006).
Rousset, D. Etude de la fraction argileuse de séquences sédimentaires de la Meuse et du Gard. Reconstitution de l’histoire diagénétique et des caractéristiques physico-chimiques des cibles. Aspects minéralogiques, géochimiques et isotopiques, PhD thesis, 270 p. (2002).
Gaucher, E. et al. ANDRA underground research laboratory: interpretation of the mineralogical and geochemical data acquired in the Callovian–Oxfordian formation by investigative drilling. Phys. Chem. Earth, Parts A/B/C. 29, 55–77 (2004).
Gaucher, E. C. et al. A robust model for pore-water chemistry of clayrock. Geochim. Cosmochim. Acta 73, 6470–6487 (2009).
Marty, N. C. M. et al. Weathering of an argillaceous rock in the presence of atmospheric conditions: a flow-through experiment and modelling study. Appl. Geochem. 96, 252–263 (2018).
Jackson, M. L. Soil chemical analysis-Advanced course, 2nd edition, llth printing. Published by the author, Madison, Wisconsin (1985)
Lanson, B. Decomposition of X-ray diffraction patterns (profile fitting): a convenient way to study clay minerals. Clays Clay Min. 45, 132–146 (1997).
Lanson, B. & Besson, G. Characterization of the end of smectite-to-illite transformation: decomposition of X-ray patterns. Clays Clay Min. 40, 40–52 (1992).
Raynolds, R. & Hower, J. The nature of interlayering in mixed-layer illite-montmorillonite. Clays Clay Min. 18, 25–36 (1970).
Moore, D. M., Raynolds, R. C. X-Ray Diffraction and the Identification and. Analysis of Clay Minerals, xviii+. 378, Oxford University Press: Oxford, New York, 1997.
Sanità, E. et al. Application of an improved TEM-EDS protocol based on charge balance for accurate chemical analysis of sub-micrometric phyllosilicates in low-grade metamorphic rocks. Clays Clay Min. 72, 1–11 (2024).
Heaney, P. J., Vicenzi, E. P., Giannuzzi, L. A. & Livi, K. J. Focused ion beam milling: a method of site-specific sample extraction for microanalysis of Earth and planetary materials. Am. Min. 86, 1094–1099 (2001).
Bardon, C. et al. Recommandations pour la determination experérimentale de la capacité d’échange de cations des milieux argileux. Rev. de. l’Inst. Francais du Pétrole 38, 621–626 (1993).
Derkowski, A. & Bristow, T. F. On the problems of total specific surface area and cation exchange capacity measurements in organic-rich sedimentary rocks. Clays Clay Min. 60, 348–362 (2012).
Neff, D., Reguer, S., Bellot-Gurlet, L., Dillmann, P. & Bertholon, R. Structural characterization of corrosion products on archaeological iron: an integrated analytical approach to establish corrosion forms. J. Raman Spectrosc. 35, 739–745 (2004).
Neff, D., Bellot-Gurlet, L., Dillmann, P., Reguer, S. & Legrand, L. Raman imaging of ancient rust scales on archaeological iron artefacts for long-term atmospheric corrosion mechanisms study. J. Raman Spectrosc. 37, 1228–1237 (2006).
Saheb, M., Neff, D., Bellot-Gurlet, L. & Dillmann, P. Raman study of a deuterated iron hydroxycarbonate to assess long-term corrosion mechanisms in anoxic soils. J. Raman Spectrosc. 42, 1100–1108 (2011).
Flude, S., Haschke, M. & Storey, M. Application of benchtop micro-XRF to geological. Mater. Mineral. Mag. 81, 923–948 (2017).
Sherman, J. The theoretical derivation of fluorescent X-ray intensities from mixtures. Spectrochim. Acta 7, 283–306 (1955).
McCrea, J. M. On the isotopic chemistry of carbonates and a paleotemperature scale. J. Chem. Phys. 18, 849–857 (1950).
Kim, S. T., Mucci, A. & Taylor, B. E. Phosphoric acid fractionation factors for calcite and aragonite between 25 and 75 C: revisited. Chem. Geol. 246, 135–146 (2007).
Murad, E. & Schwertmann, U. The influence of crystallinity on the Mössbauer spectrum of lepidocrocite. Min. Mag. 48, 507–511 (1984).
De Grave, E., Persoons, R. M., Chambaere, D. G., Vandenberghe, R. E. & Bowen, L. H. An 57Fe Mössbauer effect study of poorly crystalline γ-FeOOH. Phys. Chem. Min. 13, 61–67 (1986).
Maitte, B., Jorand, F. P., Grgic, D., Abdelmoula, M. & Carteret, C. Remineralization of ferrous carbonate from bioreduction of natural goethite in the Lorraine iron ore (Minette) by Shewanella putrefaciens. Chem. Geol. 412, 48–58 (2015).
Duboscq, J. et al. On the formation and transformation of Fe(III)-containing chukanovite, FeII2-xFeIIIx (OH)2-xOxCO3. J. Phys. Chem. Solids 138, 109310 (2020).
Neff, D., Dillmann, P., Descostes, M. & Beranger, G. Corrosion of iron archaeological artefacts in soil: estimation of the average corrosion rates involving analytical techniques and thermodynamic calculations. Corros. Sci. 48, 2947–2970 (2006).
Saheb, M. et al. Multisecular corrosion behaviour of low carbon steel in anoxic soils: characterization of corrosion system on archaeological artefacts. Mater. Corros. 60, 99–105 (2009).
Schlegel, M. L. et al. Metal corrosion and argillite transformation at the water-saturated, high-temperature iron–clay interface: A microscopic-scale study. Appl. Geochem. 23, 2619–2633 (2008).
Carrière, C. et al. Use of nanoprobes to identify iron-silicates in a glass/iron/argillite system in deep geological disposal. Corros. Sci. 158, 108104 (2019).
Patarachao, B. et al. XRD analysis of illite-smectite interstratification in clays from oil sands ores. Adv. X-ray Anal. 2, 22-31 (2019).
Lanson, B. & Champion, D. The I/S-to-illite reaction in the late stage diagenesis. Am. J. Sci. 291, 473–506 (1991).
Drissi, S. H., Refait, P., Abdelmoula, M. & Génin, J. M. R. The preparation and thermodynamic properties of Fe(II)-Fe(III) hydroxide-carbonate (green rust 1); Pourbaix diagram of iron in carbonate-containing aqueous media. Corros. Sci. 37, 2025–2041 (1995).
Reffass, M. et al. Localised corrosion of carbon steel in NaHCO3/NaCl electrolytes: role of Fe(II)-containing compounds. Corros. Sci. 48, 709–726 (2006).
Neff, D., Dillmann, P., Bellot-Gurlet, L. & Béranger, G. Corrosion of iron archaeological artefacts in soil: characterisation of the corrosion system. Corros. Sci. 47, 515–535 (2005).
Tang, Z., Hong, S., Xiao, W. & Taylor, J. Characteristics of iron corrosion scales established under blending of ground, surface, and saline waters and their impacts on iron release in the pipe distribution system. Corros. Sci. 48, 322–342 (2006).
Saheb, M., Neff, D., Dillmann, P., Matthiesen, H. & Foy, E. Long-term corrosion behaviour of low-carbon steel in anoxic environment: characterisation of archaeological artefacts. J. Nucl. Mater. 379, 118–123 (2008).
Saheb, M. et al. Iron corrosion in an anoxic soil: comparison between thermodynamic modelling and ferrous archaeological artefacts characterised along with the local in situ geochemical conditions. Appl. Geochem. 25, 1937–1948 (2010).
Pignatelli, I. et al. A multi-technique, micrometer-to atomic-scale description of a synthetic analogue of chukanovite, Fe2(CO3)(OH)2. Eur. J. Mineral. 26, 221–229 (2014).
Schlegel, M. L., Bataillon, C., Blanc, C., Prêt, D. & Foy, E. Anodic activation of iron corrosion in clay media under water-saturated conditions at 90° C: characterization of the corrosion interface. Environ. Sci. Technol. 44, 1503–1508 (2010).
Azoulay, I., Rémazeilles, C. & Refait, P. Determination of standard Gibbs free energy of formation of chukanovite and Pourbaix diagrams of iron in carbonated media. Corros. Sci. 58, 229–236 (2012).
Pandarinathan, V., Lepková, K. & Van Bronswijk, W. Chukanovite (Fe2(OH)2CO3) identified as a corrosion product at sand-deposited carbon steel in CO2-saturated brine. Corros. Sci. 85, 26–32 (2014).
Pekov, I. V. et al. Chukanovite, Fe2(CO3)(OH)2, a new mineral from the weathered iron meteorite Dronino. Eur. J. Mineral. 19, 891–898 (2007).
Azoulay, I., Rémazeilles, C. & Refait, P. Corrosion of steel in carbonated media: the oxidation processes of chukanovite (Fe2(OH)2CO3). Corros. Sci. 85, 101–108 (2014).
Stranski, I. N. & Totomanow, D. Keimbildungsgeschwindigkeit und OSTWALDsche Stufenregel. Z. Phys. Chem. 163A, 399–408 (1933).
Liu, H., Li, P., Zhu, M., Wei, Y. & Sun, Y. Fe(II)-induced transformation from ferrihydrite to lepidocrocite and goethite. J. Solid State Chem. 180, 2121–2128 (2007).
Misawa, T., Hashimoto, K. & Shimodaira, S. The mechanism of formation of iron oxide and oxyhydroxides in aqueous solutions at room temperature. Corros. Sci. 14, 131–149 (1974).
Schwertmann, U. & Fechter, H. The formation of green rust and its transformation to lepidocrocite. Clay Min. 29, 87–92 (1994).
de la Fuente, D. et al. Corrosion mechanisms of mild steel in chloride-rich atmospheres. Mater. Corros. 67, 227–238 (2016).
Song, Y., Jiang, G., Chen, Y., Zhao, P. & Tian, Y. Effects of chloride ions on corrosion of ductile iron and carbon steel in soil environments. Sci. Rep. 7, 6865 (2017).
Jambor, J. L. & Dutrizac, J. E. Occurrence and constitution of natural and synthetic ferrihydrite, a widespread iron oxyhydroxide. Chem. Rev. 98, 2549–2585 (1998).
Refait, P. & Génin, J. M. The mechanisms of oxidation of ferrous hydroxychloride β-Fe2(OH)3Cl in aqueous solution: the formation of akaganeite vs goethite. Corros. Sci. 39, 539–553 (1997).
Monnier, J. et al. Study of archaeological artefacts to refine the model of iron long-term indoor atmospheric corrosion. J. Nucl. Mater. 379, 105–111 (2008).
Monnier, J., Dillmann, P., Legrand, L. & Guillot, I. Corrosion of iron from heritage buildings: proposal for degradation indexes based on rust layer composition and electrochemical reactivity. Corros. Eng. Sci. Technol. 45, 375–380 (2010).
El Mendili, Y., Abdelouas, A., Chaou, A. A., Bardeau, J. F. & Schlegel, M. L. Carbon steel corrosion in clay-rich environment. Corros. Sci. 88, 56–65 (2014).
Schlegel, M. L. et al. Corrosion at the carbon steel-clay compact interface at 90° C: Insight into short-and long-term corrosion aspects. Corros. Sci. 152, 31–44 (2019).
Rémazeilles, C. & Refait, P. On the formation of β-FeOOH (akaganéite) in chloride-containing environments. Corros. Sci. 49, 844–857 (2007).
Peretyazhko, T. S., Ming, D. W., Rampe, E. B., Morris, R. V. & Agresti, D. G. Effect of solution pH and chloride concentration on akaganeite precipitation: Implications for akaganeite formation on Mars. J. Geophys. Res. Planets 123, 2211–2222 (2018).
Réguer, S., Dillmann, P. & Mirambet, F. Buried iron archaeological artefacts: corrosion mechanisms related to the presence of Cl-containing phases. Corros. Sci. 49, 2726–2744 (2007).
Gilbert, F., Refait, P., Lévêque, F., Remazeilles, C. & Conforto, E. Synthesis of goethite from Fe(OH)2 precipitates: influence of Fe(II) concentration and stirring speed. J. Phys. Chem. Solids 69, 2124–2130 (2008).
Mosser-Ruck, R. et al. Etude du système Verre-Fer-Argilite : rôle du pH, du redox et de la pCO2 sur la nature des phases minérales ferrifères néoformées au contact des colis et stabilité de ces phases lors d’un refroidissement entre 90° et 40°C. Andra report RP0G2R.13.001, (2013).
Rivard, C. Contribution à l’étude de la stabilité des minéraux constitutifs de l’argilite du Callovo-Oxfordien en présence de fer à 90 °C. PhD thesis, INPL Nancy, France, 338 p. (2011).
Pignatelli, I. et al. A multi-technique characterization of cronstedtite synthesized by iron-clay interaction in a step-by-step cooling procedure. Clays Clay Min. 61, 277–289 (2013).
Schlegel, M. L. et al. Microstructural characterization of carbon steel corrosion in clay borehole water under anoxic and transient acidic conditions. Corros. Sci. 109, 126–144 (2016).
Schlegel, M. L. et al. Corrosion of metal iron in contact with anoxic clay at 90 C: characterization of the corrosion products after two years of interaction. Appl. Geochem. 51, 1–14 (2014).
Le Pape, P. et al. Action of a clay suspension on an Fe(0) surface under anoxic conditions: characterization of neoformed minerals at the Fe(0)/solution and Fe(0)/atmosphere interfaces. Appl. Geochem. 61, 62–71 (2015).
Pierron, O. Interactions eau-fer-argilite: Rôle des paramètres Liquide/Roche, Fer/Argilite, Température sur la nature des phases minérales, PhD thesis, Univ. H. Poincaré, Nancy, France, 226, (2011).
Chevrier, V. Thermodynamics of clay minerals on mars: insight into the geochemical environment of early mars. In 37th Annual Lunar and Planetary Science Conference, p. 1038 (2006).
Wilson, J., Savage, D., Cuadros, J., Shibata, M. & Ragnarsdottir, K. V. The effect of iron on montmorillonite stability. (I) Background and thermodynamic considerations. Geochim. et. Cosmochim. Acta 70, 306–322 (2006).
Bourdelle, F. et al. A new view on iron-claystone interactions under hydrothermal conditions (90° C) by monitoring in situ pH evolution and H2 generation. Chem. Geol. 466, 600–607 (2017).
Belcourt, O. La perturbation chimico-minéralogique (Hydratation, état d’oxydation, eau interstitielle) de la zone perturbée excavée et ses relations avec la perturbation texturale et mécanique: application aux argilites des galeries de Bure. PhD thesis, Univ. H. Poincaré, Nancy, France, 338 p. (2009).
Vinsot, A., Lundy, M. & Linard, Y. O2 consumption and CO2 production at Callovian-Oxfordian rock surfaces. Procedia Earth Planet. Sci. 17, 562–565 (2017).
Reiss, A. G., Ganor, J. & Gavrieli, I. Size distribution and morphology of gypsum crystals precipitating from hypersaline solutions. Cryst. Growth Des. 19, 6954–6962 (2019).
Jia, C., Zhu, G., Legg, B. A., Guan, B. & De Yoreo, J. J. Bassanite grows along distinct coexisting pathways and provides a low energy interface for gypsum nucleation. Cryst. Growth Des. 22, 6582–6587 (2022).
Rivard, C. et al. Berthierine-like mineral formation and stability during the interaction of kaolinite with metallic iron at 90° C under anoxic and oxic conditions. Am. Min. 98, 163–180 (2013).
Pignatelli, I., Mosser-Ruck, R., Mugnaioli, E., Sterpenich, J. & Gemmi, M. The effect of the starting mineralogical mixture on the nature of Fe-serpentines obtained during hydrothermal synthesis at 90° C. Clays Clay Min. 68, 394–412 (2020).
Acknowledgements
This research was financially supported by the Agence Nationale pour la Gestion des Déchets Radioactifs (ANDRA). We thank the Center of Instrument Sharing for the University of Pisa (CISUP) for support with FIB sectioning and TEM imaging, and Dr. Marc Ulrich for his help in collection and treatment of μ-XRF data. This is CRPG contribution #2894.
Author information
Authors and Affiliations
Contributions
The study was conceived by N.M., Y.L., and I.P. The materials were previously produced by Y.L. and N.M. I.P., E.M., M.A., D.N., and J.M. performed sample preparation, data acquisition and analysis. I.P. wrote the paper first draft, revised by all. All authors approved the final version.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Pignatelli, I., Mugnaioli, E., Abdelmoula, M. et al. Impact of iron corrosion on the mineralogical evolution of Callovo-Oxfordian claystone: in situ MCO experiment. npj Mater Degrad (2026). https://doi.org/10.1038/s41529-026-00776-x
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41529-026-00776-x
