Corrosion Behavior and Mechanism of High-Aluminum Inconel 625 in Chlorinated Salts

Concentrated solar power plant (CSP) technology holds significant application value in the renewable energy sector for converting solar radiation into thermal and electrical energy. As a heat storage medium for next-generation solar thermal power stations, chloride salts exhibit strong corrosive effects on structural components. To enhance corrosion resistance of the heated body in molten salt environments, Inconel 625 is modified by incorporating aluminum, which facilitates the formation of a protective oxide film. In this study, High-Aluminum Inconel 625, after cold rolling and solution treatment, was immersed in a NaCl-KCl-MgCl2 eutectic chloride melt at 650 °C for 200 h. Post-corrosion analysis revealed the formation of an alumina layer on the surface, effectively mitigating corrosion. Increased aluminum content resulted in thicker alumina layers and the formation of oxidation products, such as Cr2O3, Fe2O3, MoO2, and MgCr2O4 spinel structures, significantly enhancing the alloy’s corrosion resistance. The Inconel 625 cold-rolled plate with 5.31 wt% Al exhibited the best corrosion resistance (3510 μm/year), making it a promising candidate for use in next-generation CSP heat storage and exchange components.