Study of the Influence of Surface Finishing on the Corrosion/Oxidation Behaviour of Stainless Steels in Stagnant Lead Bismuth Eutectic

Lead-bismuth eutectic (LBE) is of interest as a coolant in the design of fast reactors and also as both a coolant and a spallation target in proposed transmutation schemes for radioactive waste. However, liquid metal corrosion to the structural materials can proceed via various processes: species dissolution, formation of the inter-metallic compounds at the steels/liquid metal interface... It is known that the formation of an oxide scale on a steel surface can protect it dissolution attack by liquid LBE. The variables that play an important role on the feasibility of the formation of an oxide layer and on its protective characteristics for steels in contact with LBE are oxygen content, temperature, materials composition and evolution with time, but also surface state of steels prior to testing or weld joints, being these parameters not very widely studied. For the study of the influence of the surface finishing, specimens with different surface states were prepared (as-received, grinded, grinded and polished and electrolitically polished). These treatments gave to the materials a different degree of cold working, the higher for the mechanised samples and the lowest for the electrolitically polished. Tests were carried out at 500 and 550°C from 100 to 2000 hours with two different H2/H2O ratios: 3 and 0.03. The general conclusion is that the effect of surface finishing on the corrosion/protection processes is not significant for the conditions tested.