Corrosion Test of US Steels in Lead-Bismuth Eutectic (LBE) and Kinetic Modeling of Corrosion in LBE Systems

We present the LBE corrosion test results of several US steels, and a preliminary analysis using a kinetic model for corrosion in LBE systems. Tube and rod specimens of austenitic steels 316/316L, D9, ferritic/martensitic steels HT-9 and T- 410 and Russian martensitic steel EP823 were inserted in an LBE loop CU-1M at IPPE. The oxygen concentration in LBE was between 3-5x10-6 wt% and the flow velocity in the test sections was 1.9 m/s. The tests were performed simultaneously at 460 and 550 deg. C for 1000, 2000 and 3000 hours. Weight change, optical, SEM and X-ray analysis of the specimen performed, obtaining results on oxide film thickness, corrosion depth, microstructure and composition changes. Protective oxide films formed on the surfaces of all steels. The oxides on austenitic steels are thin compared to the oxides on ferritic/martensitic steels, which have pronounced double layer structure. T-410 specimens suffered local corrosion. Parallel to the experimental investigations, a kinetic model was developed for corrosion and corrosion product transport in oxygen controlled LBE systems. Our model incorporates the species distribution based on local thermodynamic equilibrium at the surface of structural materials into boundary conditions, and directly calculates mass transport through boundary layer diffusion and convection in the bulk flow. The model predicts drastic reduction of corrosion when oxygen in LBE is properly controlled. It also predicts complex profiles of corrosion and precipitation in flow loops that are dependent upon global conditions. This indicates that the straightforward test results may have limited applicable range if the configuration and conditions of the entire test loop are not carefully taken into account. (authors)