Insights into the corrosion mechanism of a 12Cr F/M steel in oxygen-saturated liquid LBE

The oxide scale developed on a 12Cr ferritic/martensitic steel exposed to oxygen saturated lead-bismuth eutectic (LBE) at 550 ℃ for 2000 h was investigated by multiscale characterization. It reveals that the oxide scale has a triplex structure: an outer layer, an inner layer, and an internal layer. Higher resolution analysis reveals that the internal layer is generated by the inward oxygen diffusion through grain/lath boundaries and metal lattice. The inner oxide layer is produced by the further oxidation of the residual metallic Fe and Cr2O3 precipitates in the internal layer. The outer equiaxed layer is mainly formed by the precipitation of the Fe oxides dissolved in the liquid LBE. The available space model has been further developed based on the observation of the internal layer.