针对液态Pb-Bi共晶(LBE)冷却快堆开发了一种新型高硅12Cr铁素体/马氏体钢，为进一步增强其耐Pb-Bi腐蚀性能，提升燃料组件的安全性，采用预氧化法对其进行了表面防护处理，表征了预氧化膜的结构，分析了预氧化处理对12Cr铁素体/马氏体钢耐550℃饱和氧LBE的腐蚀性能的影响。结果表明，该钢在720℃、1%O₂ + 99%N₂气氛中预氧化1 h时形成的氧化膜主要是(Fe, Cr)₂O₃和MnCr₂O₄氧化物，此氧化膜可有效阻止钢中Fe元素的向外扩散和LBE中O元素的向内扩散，进而提升了材料的耐LBE腐蚀性能。但由于Mn较高的扩散速率和在LBE中较高的溶解度，预氧化膜中的Mn元素会逐渐扩散和溶解至LBE，导致部分氧化膜失效并形成局部腐蚀区，当LBE腐蚀1000 h后，合金表面的局部腐蚀区可达60%。本工作揭示了新型高硅12Cr铁素体/马氏体钢中预氧化膜的微观结构、保护效果和失效机制，为进一步提升其预氧化膜的有效性和稳定性指明了方向。

Lead-cooled fast reactors using liquid lead or lead-bismuth eutectic (LBE) alloy coolants have attracted international attention due to their unique advantages in safety, economy, and sustainable development. The availability of suitable core materials is one of the key challenges restricting the development and application of the lead-cooled fast reactor technology. Ferritic/martensitic steel is one of the important candidates for nuclear reactor fuel cladding, but the dissolution of Cr and Ni occurs in it upon contact with high-temperature LBE, resulting in cladding failure. Adding Si can improve corrosion resistance, and based on this property, previous work developed a high-Si ferritic/martensitic steel for LBE alloy-cooled fast reactor. Recently, pre-oxidation treatment was proposed to further improve the corrosion performance of steel in contact with LBE. However, the structure of the oxide film formed after the pre-oxidation of 12Cr ferritic/martensitic steel, the effect on corrosion resistance, and the failure mechanism are not clear. In this study, a pre-oxidized film was formed on the steel surface and its structure was characterized. Steel corrosion experiments using oxygen-saturated LBE at 550^oC were also performed to analyze the influence of pre-oxidation treatment on the LBE alloy coolant corrosion resistance of steel. The results demonstrated that the oxide films formed when steel is pre-oxidized at 720^oC in 1%O₂ + 99%N₂ atmosphere for 1 h are mainly (Fe, Cr)₂O₃ and MnCr₂O₄ oxides. The oxide films can effectively prevent the outward diffusion of Fe in steel and the inward diffusion of O in LBE, thereby improving the corrosion resistance of steel to stagnant oxygen-saturated LBE alloy coolant at 550^oC. However, due to the high diffusion rate of Mn and its high solubility in LBE alloys, the Mn in the pre-oxidized film will gradually diffuse and dissolve into the LBE alloy, rendering subsequently a part of the oxide film ineffective and forming a localized corrosion zone. After 1000 h of Pb-Bi corrosion, the local corrosion area on the alloy surface can reach 60%. This study revealed the microstructure, protective effect, and failure mechanism of the pre-oxidized film on the surface of high-Si ferritic/martensitic steel, and suggested research directions for further improving the effectiveness and stability of the pre-oxidized film.