Corrosion at the carbon steel-clay borehole water interface under anoxic alkaline and fluctuating temperature conditions

Michel Schlegel (1, 2) , Sophia Necib (3) , Sylvie Daumas (4) , Marc Labat (5) , Cecile Blanc (1) , Eddy Foy (6) , Yannick Linard (3)

1 SEARS - Service d'études analytiques et de réactivité des surfaces
2 LAMBE - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement
3 ANDRA - Agence Nationale pour la Gestion des Déchets Radioactifs
4 CFG Servives - CFG Servives
5 MIO - Institut méditerranéen d'océanologie
6 LAPA - UMR 3685 - Laboratoire Archéomatériaux et Prévision de l'Altération

Coupons of carbon steel were corroded in situ in anoxic clay porewater under slightly alkaline conditions. Sample damage was less than 1 $\mu$m for 9 months at 85 °C only, and corrosion interfaces were covered by a thin, protective layer of Fe-silicate. The damage was more significant for samples exposed to room temperature transients (up to 38 μm for two years), and the long-term surface differentiated in cathodic (Fe-silicate covered) areas and anodic crevices filled with siderite, chukanovite, $\beta$-Fe$_2$(OH)$_3$Cl, and covered by tubercles. Sulfide compounds were detected, and were related to the metabolism of sulfate-reducing prokaryotes detected by microbiological techniques.

Keywords: Sulfide; Fe-silicate; Nuclear waste repository; Anoxic; Clay; Carbon steel

Domains: Material chemistry; Analytical chemistry

Michel Schlegel, Sophia Necib, Sylvie Daumas, Marc Labat, Cecile Blanc, et al.. Corrosion at the carbon steel-clay borehole water interface under anoxic alkaline and fluctuating temperature conditions. Corrosion Science, 2018, 136, pp.70-90. ⟨10.1016/j.corsci.2018.02.052⟩. ⟨cea-01736952⟩