Corrosion test of mild steel in high-temperature sodium compounds

Two different type corrosion mechanisms for the mild steel exposed to the burning sodium and its products were proposed based on the analytical results on the damaged materials in actual incident of the Japanese prototype fast breeder reactor, "Monju" and in two mockup sodium leakage and combustion tests(1). In this study, the corrosion tests on the mild steel were performed in each hypothetical melt to verify the authenticity of the proposed corrosion mechanisms. The damage of the materials in each case could be predicted accurately based on the corrosion rate which was obtained from the corrosion test in the typical conditions for the case. As the results, it, is clear that the corrosion mechanism occurred in actual incident is "Na-Fe double oxidization type corrosion" which progresses in low oxygen potential and high basicity.