Compatibility of materials for macroencapsulation of inorganic phase change materials: Experimental corrosion study

The potential of the use of salt hydrates MgCl2·6H2O (bischofite) with typical impurities of the Salar de Atacama as a thermal energy storage material was evaluated with special attention to its corrosion behavior. Bischofite behavior is compared with that of commercial salt MgCl2·6H2O. The corrosion tests were conducted with metal sheets (copper, aluminum and stainless steel) partially immersed in molten salt hydrates at a temperature of 120 °C during 1500 h. The results showed minimum corrosion on all the immersed surfaces of all the metals. However, very sever corrosion was observed at the salt/air interface due to a known phenomenon of oxygen enhanced corrosion usually found even with water at ambient temperature. The corrosion products were determined with scanning electron microscopy (SEM-EDX) and X-ray diffraction (XRD) technique. For salts hydrates bischofite and MgCl2·6H2O, the results show the formation of cuprite (Cu2O) and hematite (Fe2O3) on copper and stainless steel samples, respectively. For all cases studied in the present work, several chloride compounds were identified as corrosion products.