Electrochemical approach to predicting corrosion performance of container materials.

摘要

As part of the effort in determining the suitability of the Yucca Mountain site in Southern Nevada for emplacement of high-level nuclear waste in a repository, possible failure modes of candidate waste package container metallic materials are being investigated. Localized forms of corrosion such as pitting attack on the metal surface or attack in creviced areas are particularly pernicious failure modes that may shorten the container lifetime. The pitting potential of nickel-rich Alloy 825 are measured in chloride-containing solutions at different temperatures and adjusted to different pH values. The pitting potentials were determined by potentiodynamic polarization of Alloy 825 test specimens from the corrosion potential until a sharp increase in the electrochemical current indicated a breakdown of the protective passive film on the metal surface. Results show that Alloy 825 is susceptible to pitting attack in aggressive electrolytes containing more than 10,000 ppm chloride at 90(degree)C and acicified to a pH value less than 2.5. 5 refs., 3 figs., 1 tab.