Dynamic corrosion behaviour of stainless steel in molten salt electric heaters: Influence of film temperature under realistic flow conditions

Thermal energy storage systems using molten salts are increasingly integrated into power-to-heat (P2H) technologies to support industrial decarbonization and enhance grid flexibility. However, the long-term stability and reliability of molten salt electric heaters are limited by corrosion phenomena driven by high film temperatures and dynamic flow conditions. This study presents the development of a high-temperature dynamic test loop designed to replicate the operational environment of molten salt-based electric heaters, with a focus on evaluating corrosion mechanisms under realistic flow, temperature, and thermal boundary layer conditions. As a demonstration, SS321 was exposed to ternary Hitec salt (KNO 3 –NaNO 2 –NaNO 3 ) at bulk temperatures of 400 °C and localized film temperatures up to 530 °C for 1000 h under continuous flow. Microstructural and chemical analyses revealed excellent corrosion resistance, characterized by the formation of a dense and adherent oxide layer (∼4 μm). Differential Scanning Calorimetry and Raman microscopy confirmed the salt's eutectic composition remained stable. These results indicate that controlled film temperatures, optimized flow, and short residence times effectively mitigate degradation, validating the system design and operational strategy. The findings provide guidance for predictive corrosion modelling, material selection, and the development of durable P2H systems for industrial decarbonization. • Dynamic test loop simulates molten salt flow at up to 530 °C. • Film temperature effects analysed on oxide layers after 1000 h exposure. • HITEC salt degradation analysed for impact on SS321 corrosion rate. • Corrosion layer thickness limited to 4 μm after 1000 h dynamic test.