Corrosion Behavior of R60702 Industrial Pure Zirconium in High TemperatureNitric Acid and Propane Vapor

The corrosion behavior of R60702 industrial pure zirconium in high temperature nitric acid and propane vapor was studied by uniform corrosion test. The results show that the R60702 pure zirconium had the very low corrosion rate in nitric acid and propane vapor at 260 ℃, and a dense oxide film with thickness of about 15 μm was formed on the surface. The corrosion rate in nitric acid and propane vapor at 430 ℃ was relatively high; the surface oxide film with thickness of about 50 μm consisted of an outer loose oxide film and an inner dense oxide film; there were micro-cracks in the oxide film and part of the oxide film peeled off. The surface oxide film was mainly composed of monoclinic ZrO₂ and tetragonal ZrO₂. When the temperature was 260 ℃, the dense oxide film protected the substrate. When the temperature was 430 ℃, the protective effect of the oxide film decreased, leading to the thickening of the oxide film and stress relaxation, which caused the transformation of tetragonal ZrO₂ to monoclinic ZrO₂, expansion of the oxide film volume and generattion of micro-cracks. The cracks expanded and merged, resulting in the peeling of the oxide film.