Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions

Aluminium corrosion is a key constraint in the formulation of magnesium potassium phosphate cements (MKPC) for the effective immobilisation of this reactive metal in low- and intermediate-level radioactive waste repositories. This study examines the role of phosphate and borate species in controllin...

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Detalles Bibliográficos
Autores: Fernández-García, Carla, Alonso, M. Cruz
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2026
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/419690
Acceso en línea:http://hdl.handle.net/10261/419690
https://api.elsevier.com/content/abstract/scopus_id/105022802203
Access Level:acceso abierto
Palabra clave:Aluminium
Borate ions
Corrosion inhibition
Magnesium potassium phosphate cement
Phosphate ions
Passivation mechanism
Simulated pore solutions
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spelling Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutionsFernández-García, CarlaAlonso, M. CruzAluminiumBorate ionsCorrosion inhibitionMagnesium potassium phosphate cementPhosphate ionsPassivation mechanismSimulated pore solutionsAluminium corrosion is a key constraint in the formulation of magnesium potassium phosphate cements (MKPC) for the effective immobilisation of this reactive metal in low- and intermediate-level radioactive waste repositories. This study examines the role of phosphate and borate species in controlling passivation through electrochemical analyses in solutions representative of MKPC pore chemistries, benchmarked against OPC-like media. Electrochemical impedance spectroscopy, linear polarisation resistance, and estimated hydrogen release were used to characterise interfacial processes across ion concentrations and exposure periods. Results reveal distinct roles of phosphate and borate in aluminium passivation. Phosphate (H₂PO₄⁻, pH 4–5) at high concentrations (≥3000 ppm) drives rapid passivation via multilayer film formation, while borate (B(OH)₄⁻/H₂BO₃⁻, pH ≈8.5) becomes increasingly influential at lower levels (200–300 ppm), stabilising compact oxide films by adsorption. Mixed phosphate–borate systems reproduced the chemistry of hydrated MKPC solutions, highlighting their complementary action in establishing and maintaining passivity. Compared to OPC conditions (Ca(OH)₂, pH 12.7), which sustain active corrosion, MKPC chemistries favour stable aluminium passivation and suppress hydrogen evolution. The findings provide mechanistic insight into the inhibition processes underlying MKPC corrosion resistance and its suitability for immobilising radioactive aluminium.The authors acknowledge the funding from the European Union\u2019s Horizon 2020 Research and Innovation Program for Nuclear Fission and Radiation Protection Research (call NFRP-2019-2020 ) under grant agreement No 945098 (PREDIS) . The authors also acknowledge the support from the CSIC PIE projects No 202260E009 and No 202560E173 .Peer reviewedElsevierConsejo Superior de Investigaciones Científicas (España)European CommissionFernández-García, Carla [0009-0008-1612-4469]Alonso, M. Cruz [0000-0002-4308-9506]Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202620262026info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/419690https://api.elsevier.com/content/abstract/scopus_id/105022802203reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglés#PLACEHOLDER_PARENT_METADATA_VALUE#info:eu-repo/grantAgreement/EC/H2020/945098Electrochimica Actahttps://doi.org/10.1016/j.electacta.2025.147824Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/4196902026-05-22T06:33:51Z
dc.title.none.fl_str_mv Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
title Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
spellingShingle Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
Fernández-García, Carla
Aluminium
Borate ions
Corrosion inhibition
Magnesium potassium phosphate cement
Phosphate ions
Passivation mechanism
Simulated pore solutions
title_short Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
title_full Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
title_fullStr Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
title_full_unstemmed Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
title_sort Mechanistic role of phosphate and borate species in aluminium passivation in simulated MKPC pore solutions
dc.creator.none.fl_str_mv Fernández-García, Carla
Alonso, M. Cruz
author Fernández-García, Carla
author_facet Fernández-García, Carla
Alonso, M. Cruz
author_role author
author2 Alonso, M. Cruz
author2_role author
dc.contributor.none.fl_str_mv Consejo Superior de Investigaciones Científicas (España)
European Commission
Fernández-García, Carla [0009-0008-1612-4469]
Alonso, M. Cruz [0000-0002-4308-9506]
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Aluminium
Borate ions
Corrosion inhibition
Magnesium potassium phosphate cement
Phosphate ions
Passivation mechanism
Simulated pore solutions
topic Aluminium
Borate ions
Corrosion inhibition
Magnesium potassium phosphate cement
Phosphate ions
Passivation mechanism
Simulated pore solutions
description Aluminium corrosion is a key constraint in the formulation of magnesium potassium phosphate cements (MKPC) for the effective immobilisation of this reactive metal in low- and intermediate-level radioactive waste repositories. This study examines the role of phosphate and borate species in controlling passivation through electrochemical analyses in solutions representative of MKPC pore chemistries, benchmarked against OPC-like media. Electrochemical impedance spectroscopy, linear polarisation resistance, and estimated hydrogen release were used to characterise interfacial processes across ion concentrations and exposure periods. Results reveal distinct roles of phosphate and borate in aluminium passivation. Phosphate (H₂PO₄⁻, pH 4–5) at high concentrations (≥3000 ppm) drives rapid passivation via multilayer film formation, while borate (B(OH)₄⁻/H₂BO₃⁻, pH ≈8.5) becomes increasingly influential at lower levels (200–300 ppm), stabilising compact oxide films by adsorption. Mixed phosphate–borate systems reproduced the chemistry of hydrated MKPC solutions, highlighting their complementary action in establishing and maintaining passivity. Compared to OPC conditions (Ca(OH)₂, pH 12.7), which sustain active corrosion, MKPC chemistries favour stable aluminium passivation and suppress hydrogen evolution. The findings provide mechanistic insight into the inhibition processes underlying MKPC corrosion resistance and its suitability for immobilising radioactive aluminium.
publishDate 2026
dc.date.none.fl_str_mv 2026
2026
2026
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
Publisher's version
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/419690
https://api.elsevier.com/content/abstract/scopus_id/105022802203
url http://hdl.handle.net/10261/419690
https://api.elsevier.com/content/abstract/scopus_id/105022802203
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv #PLACEHOLDER_PARENT_METADATA_VALUE#
info:eu-repo/grantAgreement/EC/H2020/945098
Electrochimica Acta
https://doi.org/10.1016/j.electacta.2025.147824
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Elsevier
publisher.none.fl_str_mv Elsevier
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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