Corrosive behavior of saltwater phase-change materials on common refrigeration metals

Cold Thermal Energy Storage (CTES) systems often utilize phase-change materials (PCMs) such as potassium chloride (KCl) and sodium chloride (NaCl) to enhance cooling applications. However, the corrosive nature of these PCMs on common refrigeration metals, including stainless steel (St), copper (Cu), and aluminum (Al), poses a critical challenge. This study investigates the corrosion resistance of these metals in KCl and NaCl solutions (19.5% and 22.4% w/w, respectively) over a four-week period using mass loss measurements and potentiodynamic polarization tests. The results revealed that Cu demonstrated acceptable performance as an evaporator coil material, with a corrosion rate below 50 mg/cm²/year in both solutions. Conversely, Al proved unsuitable for prolonged exposure, particularly in NaCl solutions, exhibiting corrosion rates exceeding 100 mg/cm²/year. Stainless steel showed high resistance to pitting corrosion, with corrosion rates stabilizing below 100 mg/cm²/year after initial exposure. These findings offer crucial insights for optimizing material selection in CTES systems, enhancing their longevity and operational efficiency.