Corrosion of nickel-chromium-molybdenum based alloy in chloride melts containing transition metal ions

Abstract

The corrosion of KhN65MVU alloy was studied in chloride melts contained vanadium, zirconium, niobium and uranium ions and the rates of corrosion were determined for different electrolytes and temperatures. It was shown that interaction between the studied alloy and chloride melts containing transition metal ions occurs due to the oxidation of more electronegative components of the alloy by different cations from the molten salt environment. The process of oxidation is intensified at the grain boundaries where the microgalvanic pairs are formed as a result of excessive phase segregation. Anodic elements of the galvanic pairs are represented by depletion in molybdenum zones contacted with the excessive phases. It was also found that contacting KhN65MVU with niobium-containing melts results in the formation of diffusion coating on the substrate. This coating can protect the material from further oxidation by molten chloride electrolyte. Copyright © 2012 by The Electrochemical Society.