Corrosion of ferrous alloys exposed to thermally convective Pb-17 at% Li

A type 316 stainless steel thermal convection loop with type 316 stainless steel coupons and a Fe-9Cr-1Mo steel loop containing Fe-12Cr-1MoVW steel specimens circulated molten Pb-17 at% Li at a maximum temperature of 500°C. Specimens were exposed for more than 6000 h. Mass loss and surface characterization data were compared for these two alloys. At any particular exposure time, the corrosion of type 316 stainless steel by Pb-17 at% Li was more severe, and of a different type than that of similarly exposed Fe-12Cr-1MoVW steel. The austenitic alloy suffered nonuniform penetration and dissolution by the lead-lithium, whereas the Fe-12Cr-1MoVW steel tended to be more uniformly corroded. The presence of a ferritic layer on the type 316 stainless steel, and its susceptibility to spalling during specimen cleaning, were shown to be important in evaluating the data for this steel and in comparing corrosion losses for the two types of alloys. A model for the nonuniform penetration of type 316 stainless steel by Pb-17 at% Li was suggested.