Radioactive wastes from the processing of nuclear materials used for weapons production have been stored in underground carbon steel tanks for the past several decades. The waste solutions are a complex mixture of a variety of anionic and cationic species, dominated by sodium nitrates, nitrites, and hydroxide. It has been well established that localized corrosion and stress corrosion cracking of carbon steel can occur in these solutions above certain critical potentials that are determined by the anionic species and temperature. Recent studies have shown that the corrosion potential increases significantly over a period of weeks to months, such that there is a concern about exceeding the critical potentials under natural conditions of exposure. This paper discusses the evolution of the corrosion potential of steel in alkaline solutions (pH >11) in comparison to the critical potentials. The impedance behavior of the steel in these solutions shows changes in the semi-conductive behavior over time as well as the density of charge carriers that may influence the evolution of corrosion potential. The effect of the changes in corrosion potential on localized corrosion and stress corrosion cracking is discussed.