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The complex corrosion system of a medieval iron rebar from the Bourges' Cathedral. Characterization and reactivity studies
Iron reinforcements used in many medieval monuments are submitted to centuries of corrosion, and a reliable prediction of long term corrosion is needed for their conservation and restoration. This study focuses on an iron rebar from the Bourges' Cathedral (France). The corrosion product layers formed on the rebar have been investigated through SEM-EDS, Raman microspectroscopy and electrochemical measurements. The corrosion layers observed on the rebar of the Bourges' Cathedral present a multi-layered structure. The outer and the inner layers -separated by mill scale residues- have different chemical and mineralogical composition as well as different transport properties, the outer layer being apparently more permeable to impurities than the inner one. The corrosion layers on the atmosphere-side and the mortar-side are quite similar in mineralogical composition. The conditions in this thin mortar sealing are obviously intermediate between atmospheric conditions and usual conditions found in hydraulic mortars. Electrochemical reductions and composition results show reactive (oxyhydr)oxides-rich corrosion systems. The rebar corrosion layers present a relatively high reactivity due to their high content in ferrihydrite, lepidocrocite and akaganeite. In addition, the corrosion products in contact with the metal are particularly rich in ferrihydrite, which is susceptible to play the role of an oxidizing agent. This could also enhance the reactivity of the corrosion product layers. As the location of these phases could influence the reactivity, these macroscopic results should be considered in the light of microscopic observations to propose corrosion mechanism hypotheses.
The complex corrosion system of a medieval iron rebar from the Bourges' Cathedral. Characterization and reactivity studies
Iron reinforcements used in many medieval monuments are submitted to centuries of corrosion, and a reliable prediction of long term corrosion is needed for their conservation and restoration. This study focuses on an iron rebar from the Bourges' Cathedral (France). The corrosion product layers formed on the rebar have been investigated through SEM-EDS, Raman microspectroscopy and electrochemical measurements. The corrosion layers observed on the rebar of the Bourges' Cathedral present a multi-layered structure. The outer and the inner layers -separated by mill scale residues- have different chemical and mineralogical composition as well as different transport properties, the outer layer being apparently more permeable to impurities than the inner one. The corrosion layers on the atmosphere-side and the mortar-side are quite similar in mineralogical composition. The conditions in this thin mortar sealing are obviously intermediate between atmospheric conditions and usual conditions found in hydraulic mortars. Electrochemical reductions and composition results show reactive (oxyhydr)oxides-rich corrosion systems. The rebar corrosion layers present a relatively high reactivity due to their high content in ferrihydrite, lepidocrocite and akaganeite. In addition, the corrosion products in contact with the metal are particularly rich in ferrihydrite, which is susceptible to play the role of an oxidizing agent. This could also enhance the reactivity of the corrosion product layers. As the location of these phases could influence the reactivity, these macroscopic results should be considered in the light of microscopic observations to propose corrosion mechanism hypotheses.
The complex corrosion system of a medieval iron rebar from the Bourges' Cathedral. Characterization and reactivity studies
Das komplexe Korrosionssystem der mittelalterlichen Stahlarmierung in der Kathedrale von Bourges. Charakterisierung und Reaktivitätsuntersuchungen
Bouchar, M. (author) / Foy, E. (author) / Neff, D. (author) / Dillmann, P. (author)
Corrosion Science ; 76 ; 361-372
2013
12 Seiten, 13 Bilder, 4 Tabellen, 45 Quellen
Article (Journal)
English
Stahlarmierung , bewehrter Beton , Mittelalter , Bauwerk , Langzeitverhalten , atmosphärische Korrosion , Korrosionsprodukt , Oberflächenschicht , Schichtdicke , mineralogische Zusammensetzung , metallographisches Verfahren , Schichtaufbau , chemisches Reaktionsvermögen , Raman-Spektroskopie , Röntgenbeugung , intensiostatische Prüfung
| British Library Online Contents | 2013
The Cathedral of Bourges and its place in Gothic architecture
| TIBKAT | 1989
Bourges Cathedral : The west portals. Originally presented as the author's thesis, Columbia, 1968
| UB Braunschweig | 1976