One of the main concern in the development of the Gen IV lead-cooled fast reactors (LFRs) is the compatibility of the candidate structural steels and cladding materials with the heavy liquid metal (HLM). Structural materials compatibility in conditions relevant to plant operation is of primary importance to safety. The work describes performance of austenitic stainless steel AISI 321 with various surface pre-treatment exposed to liquid lead. The cylindrical specimens were pre-treated by using electro-polishing, pre-oxidation, and their combination as well as non-treated ones. Pre-oxidation was performed in argon with 30-50 Pa O2 at 450-500 °C for 14 days. Then the specimens were exposed to lead at 480 °C, flow velocity ~3 m/s and oxygen concentration 10-7 wt. % in corrosion loop MatLoo for 500 hr. The concentration of dissolved oxygen in liquid lead was controlled by mass exchange between flowing metal and argon cover gas with variable Ar ÷ 5 % H2-Ar or 10 % 02-Ar ratio. Oxygen concentration was continuously monitored using electrochemical oxygen sensors with Bi/Bi2O3 reference electrode. The Scanning Electron Microscope (SEM) with Energy Dispersive Spectroscopy (EDS) was used for post-test examination of the surfaces and cross sections of the specimens. The SEM observation demonstrated significant differences in the behaviour and in the formation of thin oxide layers of the specimens. From tested specimens the best performance showed that specimen in as-received condition while pre-oxidized specimen formed non homogeneous and non-protective oxide layer and electro-polished specimen showed vulnerability to intergranular corrosion attack.Keywords: Loop MatLoo, AISI 321, forced circulation, lead coolant, corrosion
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