Coatings for Heat Storage Reactors with Hygroscopic Salts

One of the bottlenecks for realizing a commercial system for thermochemical heat storage using hygroscopic salts is corrosion induced by chemical side-reactions. E.g. when Na2S hydrates are used, we basically deal with corrosion caused by the production of the volatile H2S, threatening metal parts in the reactor and the vacuum system. Based on comparison with similar corrosion problems, epoxy coatings were selected to protect metal parts.Because of the complex geometry of the heat exchanger, e-coating was selected as application method. Applied coatings were tested by electrochemical impedance spectroscopy and by visual inspection. We found that flat areas were well covered, while defects were observed around edges and connections.