Oxide layer stability in lead-bismuth at high temperature

Materials protection by 'in situ' oxidation has been studied in stagnant lead-bismuth, with different oxygen levels (H-2/H2O ratios of 0.3 and 0.03), at temperatures from 535 degreesC to 600 degreesC and times from 100 to 3000 h. The materials tested were the martensitic steels F82Hmod, EM10 and T91 and the austenitic, stainless steels, AISI 316L and AISI 304L. The results obtained point to the existence of an apparent threshold temperature above which corrosion occurs and the formation of a protective and stable oxide layer is not possible. This threshold temperature depends on material composition, oxygen concentration in the liquid lead bismuth and time. The threshold temperature is higher for the austenitic steels, especially for the AISI 304L, and it increases with the oxygen concentration in the lead-bismuth. The oxide layer formed disappear with time and, after 3000 h all the materials, except AISI 304L, suffer corrosion, more severe for the martensitic steels and at the highest temperature tested. (C) 2004 Elsevier B.V. All rights reserved.