Long term immersion corrosion tests on metal-PCM pairs used for latent heat storage in the 24 to 29°C temperature range

Abstract

Phase Change Materials (PCMs) can be used for heating and cooling in buildings with two applications in mind. First, using natural heat and cold sources, that is solar energy for heating or night cold for cooling. Second, using manmade heat or cold sources more efficiently. In any case, storage of heat or cold with PCMs is necessary to match availability and demand with respect to time and also with respect to power. Depending on where and how the PCM is integrated, PCMs with different melting points are applied. Currently, there is a lack of commercial PCMs in the lower temperature range, that is between 5 and 29°C. The research to develop such materials is bringing new PCMs to the market, but they should be tested before application. Their corrosion behaviour is one of the aspects to be considered. In the present work, we tested the corrosion resistance of five commercial metals in contact with PCMs with a melting temperature in the range of 5 to 29°C in experiments with a duration up to 500 days. The PCMs were a commercial one, TH29 from TEAP (Australia), with a chemical composition of CaCl2·6H2O and an unknown nucleator, and the mixture of this material with MgCl2·6H2O (2:1wt%) to obtain a new PCM with melting temperature around 23°C. The main conclusions to be taken were that aluminum and steel should not be used in combination with these PCMs, but all the other metals have shown no problems. Maybe, only the fact that stainless steel can produce some orange precipitate, together with former literature recommendations to avoid the use of this metal, should be highlighted.