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

Abstract : 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 (Fe$_3$O$_4$) formed during the first immersion days. For longer immersion times (90 days) in cement slurry, hydroandradite (HA) (Ca$_3$(Fe$^{3+}$)$_2$(SiO$_4$)$_y$(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 slowing down corrosion can form.