SUMMARYThis report describes a study in which neutron-activated 347 stainless steel was exposed to surficial sediment from a site in the Hatteras Abyssal Plain of the Northwest Atlantic Ocean. This sediment consists of -20% CaC0 3 , a comparatively large amount of carbonate which could lead to the formation of calcareous scale on the metal surface and reduce the corrosion rate. The distribution of indigenous metals among different chemical fractions shows that -50-60% of extractable Cr, Mn, Fe, Co, and In were associated with amorphous Mn and Fe oxides. Most of the remaining extractable Cr (-40%), and about a third of the extractable Cu appear to have been weakly complexed. Major fractions (25-36%) of extractable Mn, Co and Ni were present as adsorbed cations. Organic complexation appears to account for a large amount (25-40%) of extractable Fe, Ni, Cu and In.Neutron-activated 347 stainless steel specimens were exposed to sediment slurry under aerobic and non-oxygenated conditions for a period of 94 days. The redox potential measurements for air-sparged and N 2 , CO 2 -sparged sediment slurries were +410 and +60 mv, respectively, at the end of the experimental period. The presence of O 2 produced increased amounts of corrosion products: 3.2 ~g year-1 cm-2 were released into aerated sediment and 1.0 ~g year-1 cm-2 were released when O 2 was absent.Using chemical extraction to define partitioning of corrosion products showed that relatively labile substances constituted about 84% of the 60CO activity released in aerated sediment. Materi al s extracted by DTPA, 1 i kely adsorbed cations, are most promi nent, accounting for 57% of the labile material. Smaller fractions «15%) of the released corrosion products as measured by 60CO activity were found in organically complexed or oxidic materials.Relatively labile substances constitute about 82% of the total 60Co activity released under non-oxygenated conditions. Of this material almost 25% is present in soluble or easily dissolved forms.In non-oxygenated compared with aerated sediment, a larger fraction of material was soluble or easily dissolved and less was removed by treatment with DTPA (27% vs 48%). Thus, a large fraction of 60Co which was in the soluble or easily dissolved forms under non-oxygenated conditi ons appears to have been more strongly adsorbed to the sediment under aerated conditions. The fractions of corrosion products associated with sediment organic and oxidic materials is about the same (12 to 14%) under either redox condition .