Effect of Si addition on the oxidation of a 12Cr1Al ODS alloy in liquid LBE

The corrosion behavior of Fe-12Cr-1Al oxide dispersion strengthened (ODS) alloys, with and without 2 wt% Si addition, was examined in oxygen-controlled (10$^{−6}$ wt%) liquid lead–bismuth eutectic (LBE) at 650 °C for 2000 h. Both alloys developed protective surface scales that suppressed dissolution attack, covering nearly the entire exposed surface. For the Si-containing alloy, the oxide scale was thinner and more compact, accompanied by the formation of a discontinuous SiO$_2$ layer at the interface between the outer and inner oxides. This interfacial SiO$_2$ impeded the outward diffusion of Fe and Cr while facilitating Al outward transport, leading to denser (Fe,Al)$_3$O$_4$ spinels in the outermost layer and a reduced defect density within the Al$_2$O$_3$-rich inner layer. A dissolution–oxidation–redeposition mechanism was proposed to rationalize the evolution of the multi-layered scales. These findings demonstrate that minor Si additions enhance the compactness and protectiveness of oxide scales on ODS alloys, offering guidance for the design of corrosion-resistant structural materials for LBE-cooled systems.