Reclamation Information Sharing Environment (RISE)

Reclamation scientists conducted field trials of various protective linings at the Shasta Dam Unit 5 Penstock (Shasta) in 1949 and at the Collbran Project Salt Creek Siphon (Collbran) in 1959. The results of the first investigation since 1972 where Shasta and Collbran are evaluated together are reported here. Researchers used data from visual assessments and electrochemical impedance spectroscopy (EIS) to evaluate the current performance of surviving test linings at Shasta and Collbran. Visual inspections found 13 Collbran lining systems exhibited no or minimal damage after 63 years. EIS data was combined with visual inspection results to investigate how dielectric characteristics might be related to the visual appearance of the test linings by applying an equivalent circuit model (ECM) to each lining system. The findings demonstrate certain formulations containing coal-tar, red lead, vinyl, chlorinated rubber, or epoxy mastic can provide corrosion protection for over 50 years of service. Future work includes experimental validation of ECM results with quantitative elemental mapping of long-term coating test panels; correlation of ECM results to corrosion rates and degradation mechanisms; identification of thresholds for EIS data and/or ECM results and validation of ECM for field EIS data.