Molten salt thermal energy storage (TES) tanks operate under extreme thermo‑mechanical and chemical conditions due to high temperatures, cyclic loading, and prolonged exposure to corrosive salt environments. This study presents a coupled corrosion‑based design and numerical investigation of stress evolution in a hot molten salt storage tank using finite element analysis. A three‑dimensional thermo‑mechanical model is developed to capture transient and steady‑state temperature fields, thermal gradients, and resulting stress distributions during charging and discharging cycles. Temperature‑dependent material properties and realistic boundary conditions representative of industrial‑scale TES systems are applied. Corrosion‑induced degradation is incorporated through progressive wall‑thickness reduction based on experimentally reported corrosion rates for sodium hydroxide salt. The results indicate that stainless steel tanks experience significantly higher stress levels compared to Inconel tanks, with a pronounced increase in primary stresses in the later years of operation due to material loss. The proposed modelling framework provides a robust tool for lifetime‑oriented design, material selection, and structural assessment of molten salt storage tanks, supporting the development of safer and more cost‑effective high‑temperature thermal energy storage systems.