Anticorrosive PEO coatings on metallic cast heat enhancers for thermal energy storage

ABSTRACT

The research aims to determine whether a protective oxide coating obtained by plasma electrolytic oxidation (PEO) will prevent unfavourable changes occurring on the surface of aluminium heat enhancers for thermal energy storage (TES) based on phase change materials (PCMs). For domestic purposes (short-term, solar energy), salt hydrates are widely utilised as PCMs. Their low thermal conductivity makes the application of metal enhancers necessary to improve heat transfer in the unit. Due to the chemically aggressive nature of MgCl₂·H₂O, aluminium enhancers can be negatively affected during working cycles. PEO was proposed to overcome corrosion issues in the units. Cast samples, coated with PEO for a short time in KOH-Na₂SiO₃ electrolyte, were subjected to a molten MgCl₂·H₂O environment. Mass change and the surface were studied via SEM, EDS, and XRD measurements. A thin layer of aluminium oxide prevented castings from changes occurring on the surface of the enhancer.

KEYWORDS:

• plasma electrolytic oxidation
• thermal energy storage
• phase change materials
• aluminium
• silicon
• heat enhancers
• corrosion
• prolonged exposure to aggressive environment

Acknowledgements

The authors would like to thank Department of Mechanics, Materials and Biomedical Engineering, Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, for the possibility to perform XRD measurement, for their help and support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work has been developed in the frame of the ASTEP project, funded by the European Union’s Horizon 2020 research programme under grant agreement N◦ 884411.