Corrosion assessment of promising hydrated salts as sorption materials for thermal energy storage systems

Salt hydrates are an appealing option to be used as sorption materials in thermal energy storage (TES). In this work, strontium bromide and magnesium sulphate have been selected as one of the most promising salt hydrates since they present high energy storage density (>130 kWh/m(3)) and efficiency (>20%). One of the main drawbacks of sorption materials rely on control the hydratation-dehydratation process but there are other parameters that can modify this behaviour as the corrosive potential of these salts in contact with the container material selected for the application. Hence, four different metal container materials, specifically stainless steel, copper, aluminium, and carbon steel have been tested in SrBr2 center dot 6H(2)O and MgSO4 center dot 7H2O hydrate salts, during 100 h at dehydratation conditions. After the gravimetric and micrograph analysis carried out via scanning electron microscopy (SEM) study, only carbon steel is not recommended for this application in contact with SrBr2 center dot 6H(2)O, obtaining a corrosion rate of 0.038 mm/year, with a metallographic corrosion layer thickness of 25.2 mu m. Aluminium, copper and stainless steel showed a better corrosion resistance also in SrBr2 center dot 6H(2)O and MgSO4 center dot 7H(2)O with corrosion rates below 0.008 mm/year.