Abstract
Molten salts have emerged as viable candidates for thermal energy storage in Concentrated Solar Power (CSP) applications. Candidate chloride salts offer the advantages of being readily available and stable at high temperatures, thus opening up the possibility for increased power generation efficiency. However, molten chloride salts are corrosive; therefore, proper materials selection for plant hardware is vital. Current CSP plants use stainless steels and nickel-base alloys as materials of construction because of the desirable combination of mechanical properties and corrosion resistance. In this research project, the focus was on the corrosion behavior of two different stainless steels (UNS S30400 and UNS S31600) and a carbon steel, i.e., UNS G10180. These were tested at 700°C in a molten NaCl-KCl-MgCl2 eutectic salt in static air and flowing argon. Electrochemical techniques were used to characterize the corrosion behavior of these materials. The morphology of the attack was determined using scanning electron microscopy coupled with energy dispersive spectroscopy (EDS). X-ray diffraction was used to characterize the corrosion products formed on the surface of the substrate. Based on these results, the candidate salt was deemed to be unsuitable for this application. In addition, all of the candidate alloys had unacceptably high corrosion rates.
