Corrosion behavior of iron plates in cementitious solution at 80 °C in anaerobic conditions

Iron was corroded in anoxic cementitious (pH 13.2) media (filtered porewater or cement slurry) at 80 °C; corrosion products were investigated by microscopic techniques. A thin film of magnetite (Fe3O4) formed during the first immersion days. For longer immersion times (90 days) in cement slurry, hydroandradite (HA) (Ca3(Fe3+)2(SiO4)y(OH)4(3-y)) formed a dense outer layer and an heterogeneous inner layer. A thin oxide layer is always observed in contact with metal and is believed to correspond to a protective barrier. Our results suggest that in the conditions of the Belgian supercontainer for radioactive waste disposal, a passive layer can form slowing down corrosion.