Studies on the corrosion and mechanical behavior of TiCode-12 and other titanium alloys to be used as candidate canister or overpack barriers in a high-level waste (HLW) repository or test facility in salt have been in progress at Sandia National Laboratories since 1976. Titanium alloys were selected as the primary materials for detailed testing based on candidate screening analyses (general corrosion and economic assessments) of ∼20 different alloys. The corrosion behavior of TiCode-12 has been evaluated as a function of: brine composition, temperature, time, pH, oxygen concentration, and gamma radiolysis. Uniform corrosion rates are in the range of 0.1 to 10 µm/yr; no significant pitting or crevice corrosion has been observed. This can be compared to the long-term measured rate of 0.13 mm/yr for ductile cast iron in Brine A, analyzed as a corrosion-allowance canister material. The highly adherent, passivating titanium oxide film that provides the corrosion protection has been evaluated via electrochemical polarization and surface analysis techniques to enable modeling of the corrosion mechanism(s). An increase in the corrosion rate by a factor of ∼2 was observed for sensitized TiCode-12; the rate appears to be modified by the Ti2Ni intermetallic phase and iron impurity content. Alterations in the composition and processing procedure of TiCode-12 have been evaluated to optimize corrosion, mechanical, and mill-producibility properties for HLW package applications. Slow strain rate testing of TiCode-12 revealed no apparent susceptibility to stress corrosion cracking; no significant changes in tensile properties were observed, but alterations in fracture mode were determined to be caused by internal hydrogen content. Some embrittlement occurs at hydrogen concentrations in the range of 200 to 300 ppm by weight (wppm), but the macroscopic mechanical properties of TiCode-12 are not significantly affected at concentrations up to 1100 wppm. Further research on slow crack growth threshold stress intensity as a function of hydrogen content is required before any hydrogen content limit can be imposed. Based on the analysis of available corrosion and metallurgical results, an all-TiCode-12 HLW canister package for use in a repository or test facility in salt is being proposed. Such a simplified HLW canister could provide long-term containment integrity and significantly minimize total HLW isolation system costs when compared to other waste package design concepts.