Selective surface preoxidation to inhibit the corrosion of AISI type 316L stainless steel by liquid Pb-17Li

This paper describes the formation of a ternary oxide coating on 316L stainless steel from the reaction of Pb-17Li with the preoxidized surface of steel specimens. The preoxidized surfaces were prepared by heating 316L stainless steel specimens to 800deg C in a controlled H2/H2O atmosphere (ratio 1000:1). The oxide layer before reaction with the Pb-17Li was characterized as Mn1.5Cr1.5O4. Analysis after reaction with Pb-17Li indicated a LiMn2O4 structure with some of the manganese sites occupied by chromium. 316L specimens prepared with different oxide layer thicknesses, along with uncoated specimens, were corroded in the isothermal hot legs of two Pb-17Li filled thermal convection loops. Post-test analysis of the specimens indicated that the oxide coated specimens had, on average, a thinner ferritic corrosion layer than the uncoated specimens. The coated specimens also showed areas with no ferritic corrosion layer. (orig.)