Mortazavi, A.N.Zhao, Y.Esmaily, MAllanore, A.Vidal, J.Birbilis, Nick2025-02-102025-02-100927-0248https://hdl.handle.net/1885/733735174There is currently an ever-increasing demand for higher process efficiencies in next generation (Gen3) concentrating solar power (CSP). Higher process efficiencies may be procured by increasing the operating temperature, and simultaneously, minimizing the degradation of materials used for construction of CSP plants (e.g., piping, thermal storage tanks, solar receivers and heat exchangers). Thus, understanding materials corrosion in the presence of molten salt mixtures used as thermal energy storage media and heat transfer fluids is indispensable for CSP development. The present paper provides insights into the effects of salt purification on the corrosion of a nickel-based alloy (Haynes 230) isothermally exposed to a stagnant chloride-based salt mixture at 800 °C. The MgCl2-based salt mixture was thermally dehydrated and chemically treated with (0.1 and 0.5 wt %) elemental magnesium. Results reveal the electrochemical nature of the corrosion process, and the formation of corrosion products such as oxides (MgO, MgCr2O4, and MgAl2O4) and nitrides (CrN) on the alloy surface and in sub-surface regions. Magnesium additions enhanced the ability to resist corrosion by reducing the concentration of impurities (H2O, MgOH+, OH− species) and polarizing the alloy surface. The formation of nitrides in all cases studied indicates the impact of using nitrogen as a protective gas in the system. Results also reveal that a single step treatment of the salt using metallic Mg could be considered as a measure to control the salt's impurity level, e.g., if required for system control.The authors are grateful for financial support from the Swedish Research Council and the Royal Swedish Academy of Engineering Sciences. M.E. is especially thankful for the generous support to the Helge Ax:son Johnsons stiftelse, Stockholm, Sweden. Parts of the present investigation was carried out in the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. This material is based upon work supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under the Solar Energy Technologies Office Award Number 33870. Additional funding was provided by U.S. Department of Energy's Office of Science and Office of Workforce Development for Teachers and Scientists (WDTS) under the Community College Intern-ship (CCI) program and the Science Undergraduate Laboratory Intern-ship (SULI) program.application/pdfen-AU©2021 The authorsHigh-temperature corrosionConcentrating solar powerMagnesiumOxidation and nitridationCathodic protection202210.1016/j.solmat.2021.1115422024-01-07