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.