D. B. Mitton

There is a need both to destroy hazardous military and civilian waste and to identify safe and efficient alternative technologies. One effective process for the destruction of such waste is supercritical water oxidation (SCWO); however, materials degradation issues are one of the central challenges to this technology. It became apparent a number of years ago that maintaining a region thermodynamically favorable to alloy stability through feed stream modification could reduce degradation due to corrosion. However, a need for feedback from in-situ potential and pH electrodes was also recognized. This collaboration covered both the evaluation of corrosion phenomena in SCWO systems as well as the development of high temperature high pressure potential and pH electrodes for use in SCWO systems. Ultimately, the efficacy of feed chemistry control for SCWO systems was demonstrated during the project.

Summary During the Workshop on Corrosion in SCWO Systems held at MIT in 1993 the attendees recognized the potential for corrosion to restrict the commercialization of SCWO for aggressive waste streams. At that time, the group consensus was that a material of fabrication universally applicable to all sections of a SCWO system was extremely unlikely [8]. As presented in this review, while the database for the potential materials of fabrication for SCWO systems has increased significantly since then, the group consensus apparently still holds. The corrosion of the materials of fabrication remains a serious concern and a significant amount of research remains to be carried out to identify materials or methods to reduce degradation within all sections to an acceptable level.