Immersion corrosion tests on metal-salt hydrate pairs used for latent heat storage in the 32 to 36 8C temperature range
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During the last decades, energy storage has become more and more important. It is required in order to utilize alternative energy sources, which often are available at times when energy is not needed. The main applications of PCMs (Phase Change Materials) in thermal energy storage are when space restrictions limit larger thermal storage units. But widespread use of latent heat stores has not been realized till today due to two main problems: the low heat flux, and the insufficient long term stability of the storage materials and containers. In the present work, we studied this second problem selecting different common metals (aluminum, brass, copper, steel, and stainless steel) and testing their corrosion resistance in contact with salt hydrates that are used as PCMs (zinc nitrate hexahydrate, sodium hydrogen phosphate dodecahydrate, calcium chloride hexahydrate). The method used was the immersion corrosion test. The tests here presented and evaluated were short term. As a consequence of the results from the experiments several pairs can be ruled out. The combinations of zinc nitrate hexahydrate with stainless steel, sodium hydrogen phosphate dodecahydrate with brass, copper and stainless steel, and calcium chloride hexahydrate with brass and copper shared no significant corrosion in the short term and should be studied further.