Large-scale testing of corrosion mitigation strategies for molten salts at concentrated solar power plants

Most of the Concentrated Solar Power (CSP) plants rely on molten salts as heat transfer fluids and thermal energy storage mediums due to their high thermal stability and efficiency. However, the long-term performance and economic viability of CSP systems are significantly affected by the corrosive nature of molten salts. This study investigates the efficiency of three anti-corrosion methods applied to carbon steel exposed to molten Solar salt in a large-scale experimental setup (~380 kg of salt). The materials were analysed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and mass variation to assess the extent and mechanisms of corrosion. Our results demonstrate distinct corrosion patterns and rates dependent on the applied anti-corrosion methods. In particular, spray-graphitization and nanoparticle coating revealed a 4-fold and ~20% reduction of the corrosion rate, while laser-texturing was inefficient in protecting carbon steel from Solar salt corrosion attack. This large-scale study provides an important insight into the selection and development of more resilient materials and methods under conditions where saturation of chemical reactions due to salt contamination cannot occur due to large quantities of molten salt. The findings underscore the importance of comprehensive, large-scale testing to understand and mitigate the challenges posed by molten salt corrosion in industrial applications.