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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/231307
Caracterización de materiales bajo ensayos de corrosión, para su aplicación como medio de almacenamiento de energía
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The increasing development of concentrated solar power (CSP) technologies has reinforced the need for reliable thermal energy storage (TES) systems capable of operating under high-temperature and chemically aggressive environments. In this context, molten nitrate salts, particularly Solar Salt composed of 60 wt.% NaNO₃ and 40 wt.% KNO₃, are widely used as heat transfer and storage media due to their suitable thermophysical properties. However, prolonged exposure of metallic components to molten salts may promote oxidation, corrosion and surface degradation, compromising the durability, safety and long-term efficiency of TES systems. Therefore, the application of protective coatings represents a relevant strategy to improve the performance of structural materials used in CSP plants.
This work evaluates the corrosion behaviour of 316L stainless steel coated with AlTiN and AlCrN by physical vapour deposition (PVD), with the aim of assessing their potential application as protective barriers in thermal energy storage systems. The coated samples were exposed to commercial Solar Salt under static isothermal conditions at 450 °C for 1200 h. The materials were characterized before and after corrosion testing by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). In addition, a two-dimensional steady-state thermal simulation was developed in ANSYS to analyse the influence of the micrometric coatings on heat transfer through a representative multilayer wall section of a TES tank.
Prior to corrosion exposure, both coatings showed continuous and relatively homogeneous cross-sectional morphologies. The AlTiN coating presented an average thickness of approximately 3.72 μm, while the AlCrN coating exhibited a higher average thickness of approximately 4.92 μm, indicating good coating uniformity over the 316L substrate. After exposure to molten Solar Salt, SEM observations revealed noticeable surface modifications in both systems, including dark irregular regions and localized deposits, which may be associated with oxidation/corrosion products or salt-derived residues. EDS analyses showed high oxygen contents together with significant Fe, Cr and Ni signals, suggesting the participation of the stainless steel substrate and the formation of oxidized regions. Minor Na and K signals further indicated interaction with the molten salt environment.
The XRD patterns obtained after corrosion were mainly dominated by Fe-Cr-Ni phases associated with the 316L substrate, while no clear diffraction peaks attributable to the original AlTiN or AlCrN coatings were conclusively identified. This behaviour may be related to the low volumetric contribution of the coatings, peak overlapping with the substrate, partial degradation of the coating layers or the formation of poorly crystalline corrosion products. The thermal simulation showed nearly identical heat flux values for both coated systems, indicating that, due to their micrometric thickness, the coatings have a negligible effect on the overall heat transfer of the tank wall. Therefore, their main contribution should be understood as protective rather than thermal-insulating.
Overall, the results indicate that both AlTiN and AlCrN coatings were affected by prolonged exposure to molten Solar Salt. Nevertheless, AlCrN showed a potentially more favourable protective behaviour due to its higher initial thickness and chromium-containing composition. Further studies involving gravimetric measurements, Raman spectroscopy, XPS, grazing-incidence XRD and adhesion tests are recommended to confirm the corrosion products and quantify the protective efficiency of each coating
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Treballs Finals del Màster d’Energies Renovables i Sostenibilitat Energètica, Facultat de Física, Universitat de Barcelona. Curs: 2025-2026 Tutors: Sergi Dosta Parras, Lorena Betancor Cazorla
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COELLO PÉREZ, Nicolás. Caracterización de materiales bajo ensayos de corrosión, para su aplicación como medio de almacenamiento de energía. [consulted: 10 of September of 2026]. Available at: https://hdl.handle.net/2445/231307