Abstract: Inconel 625 flux cored welding wire is widely used in the repair of solar energy storage pipelines due to its excellent corrosion resistance. In the application environment of high-temperature chloride molten salt pipelines, the repaired pipeline surface is prone to salt film deposition, leading to high-temperature thermal corrosion. In order to study the hot corrosion mechanism of Inconel 625 overlay metal, MAG welding was used to stack Inconel 625 overlay metal. Explore the corrosion behavior of Inconel 625 clad metal in MgCl₂-KCl molten salt at 600 ℃ -800 ℃. Research has shown that the lattice constant of Inconel 625 deposited metal decreases with increasing temperature. At the same time, this article establishes an element diffusion model for Inconel 625 clad metals to describe the diffusion behavior of Cl, Ni, and Cr elements after corrosion. The diffusion model was simulated based on partial differential equations and initial boundary conditions. The diffusion coefficients of Cl, Ni, and Cr elements in Inconel 625 clad metal at 800 ° C were calculated to be 7.68 × 10^-14 cm²·s^-1, 6.78 × 10^-14 cm²·s^-1, and 7.34 × 10^-14 cm²·s^-1, respectively. The corrosion of Inconel 625 deposited metal by chloride molten salt is mainly related to the diffusion and dissolution of Cr element and the invasion of Cl^-. The higher the diffusion coefficient, the worse its corrosion resistance.