Ten years of Toarcian argilite -carbon steel in situ interaction

In situ interaction experiments over periods of 2, 6, and 10 years between Toarcian argillite and carbon steel discs were carried out in the Tournemire Underground Research Laboratory (URL), yielding a dataset of the materials’ geochemical evolution under conditions representative of the future geological disposal of high-level long-lived radioactive wastes. The carbon steel discs were exposed to corrosion due to trapped oxygen. The corrosion rates indicate that the oxidizing transient lasted between 2 and 6 years. A systematic dissolution of calcium phases (Ca- smectite sheets in I/S and calcite) was observed in the iron diffusion halos. The iron release induced mineralogical dissolution and precipitation reactions, which partly clogged the argillite porosity.