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...
| Autores: | , |
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| 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 |
| Sumario: | 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. |
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