Sandra Taylor¹, Timothy G Lach¹, Matthew J Olszta¹, Karen Kruska¹, Danny J Edwards¹, Thak Sang Byun¹, Daniel K Schreiber¹; ¹Pacific Northwest National Laboratory

In this study we probe atomic transport mechanisms driving corrosion and material degradation under irradiation at the nanoscale using correlative scanning transmission electron microscopy (STEM) and atom probe tomography (APT). In particular the formation and evolution of passivating oxide layers during stress corrosion cracking on neutron irradiated 304 stainless steel is investigated. The analyses reveal a complex interplay of corrosion- and radiation-induced elemental segregation and defect formation impacting the nature of the passivating films. Nominally protective thick oxide films can form but still penetrate into the alloy via linear defects and dislocation loops, while other surfaces form thin oxide films that effectively passivate on less defective surfaces. Experiments using isotopic tracers and APT are also being developed to probe oxide formation mechanisms, in turn providing insight into oxide passivity and atomic transport through the passive films under irradiation.