An oxidation treatment, often termed “pre-oxidation”, is performed on austenitic stainless steel prior to glass-to-metal (GTM) joining to produce hermetic seals. The resulting thin oxide acts as a transitional layer and a source of Cr and other elements which diffuse into the glass during the subsequent bonding process. Pre-oxidation is performed in a low pO₂ atmosphere to avoid iron oxide formation and the final oxide is composed of Cr₂O₃, MnCr₂O₄ spinel, and SiO₂. Significant heat-to-heat variations in the oxidation behavior of 304L stainless steel have been observed, which result in inconsistent GTM seal behavior. The objectives of this work were to characterize the oxidation kinetics, the oxide morphology and composition, and the stainless steel attributes that lead to robust GTM seals. The oxidation kinetics were determined by thermogravimetric (TG) analysis and the oxide layers were characterized using metallography, SEM, focused ion beam (FIB) analysis, and x-ray diffraction (XRD). The results show that poor sealing behavior is associated with slower oxidation kinetics and a more continuous layer of SiO₂ at the metal/oxide interface. In addition, the effects of 304L heat composition on oxidation behavior will be discussed and a framework is developed for selecting stainless steels for GTM seal applications. * Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Dept. of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000