Anticorrosive AlN coatings for heat exchangers in thermal energy storage systems

• Published in: Thermal science and engineering progress 2023-08, Vol.43, p.102014, Article 102014
• Main Authors: Panagiotopoulos, N.T., Lekatou, A.G., Agrafioti, K.A., Prouskas, C.C., Koukou, M.K., Konstantaras, J., Lymperis, K., Vrachopoulos, M.Gr, Evangelakis, G.A.
• Format: Article
• Language: English
• Subjects: Aluminum nitride coating; Anticorrosive coatings; Heat exchanger; Phase change materials; Potentiodynamic polarization; Thermal performance
• ISSN: 2451-9049; 2451-9049
• DOI: 10.1016/j.tsep.2023.102014

•Magnetron sputtered thermally conductive aluminum nitride (AlN) coatings.•Anticorrosive protection for engineering applications related to thermal storage.•Anticorrosive behavior of AlN coatings on commercial aluminum against corrosive salt hydrates.•Thermal and anticorrosive evaluation of AlN coated heat exchanger (HE)•Enhanced thermal performance of AlN coated HE, exhibiting faster charging/discharging cycling process. Salt hydrates are commonly used as buffer materials in thermal storage applications. One of the major problems usually encountered is corrosion issues related with the heat exchanger (HE) materials that are in contact with them. In this study we report results demonstrating a way for addressing this problem by means of thin film coating of the heat exchanger. Nanostructured AlN films that can be easily grown by an industrially accessible process, i.e. magnetron sputtering, can guarantee high thermal conductivity requirements, in conjunction with high resistance to both uniform and localised corrosion compared to the Al substrate. The properties of the films that were grown were evaluated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron microscopy (XPS). In addition, reverse polarization was employed to assess their corrosion performance, while charging-discharging temperature versus time monitoring was used to establish their behaviour in real working conditions. It came out that the coated heat exchanger exhibits better thermal behaviour than the uncoated one, namely faster charging/discharging, smaller supercooled region and smaller overall duration of the cycling process. The present results suggest that the AlN coatings developed herein can be used for the protection of structural elements used in thermal storage applications.