Study on the Corrosion Behavior of inconel 625 deposited metal against molten nitrate

Abstract

In order to investigate the corrosion resistance of Inconel 625 deposited metal under two conditions of isothermal and thermal cycling in nitrate molten salt, this paper conducted nitrate molten salt tests on its alloy at alternating temperatures between 565 ℃ and 290 ℃-565 ℃. By using SEM, XPS and other methods to characterize the corroded samples, it was found that the corrosion amount of the deposited metal under isothermal conditions was higher than that under thermal cycling conditions. The results showed that compared to corrosion under isothermal conditions, the corrosion weight loss of Inconel 625 deposited metal under thermal cycling conditions was 0.536×10−3 mg/mm2, 0.714×10−3 mg/mm2, 0.1429×10−2 mg/mm2, and 0.232×10−2 mg/mm2, respectively, which were smaller than those under isothermal conditions of 0.1×10−2 mg/mm2, 0.13×10−2 mg/mm2, 0.2×10−2 mg/mm2, and 0.35×10−2 mg/mm2. The corrosion rate under thermal cycling conditions was maintained at approximately 0.228×10−3 μm/h, while under isothermal conditions, the corrosion rate ranged from a minimum of 0.427×10−3 μm/h to a maximum of 0.1458×10−2 μm/h. Through observation, layers of Cr2O3, NiO, and Fe2O3 were identified. The intermediate layer of Fe2O3 plays a protective role against potential dissolution triggered by the molten salt in the inner Cr2O3 and NiO layers.