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Title: Corrosion resistance of MCrAlX coatings in a molten chloride for thermal storage in concentrating solar power applications

Corrosion evaluations of Incoloy 800 H (In800H) and stainless steel AISI 310 (310SS), in bare and coated conditions, were performed in 34.42 wt% NaCl – 55.47 wt% KCl at 700 °C in a nitrogen atmosphere. This NaCl–KCl composition has a melting point of 657 °C, which makes it suitable for latent-heat thermal energy storage in concentrating solar power applications. Several nickel-based MCrAlX coatings were tested, where M = Ni and/or Co and X = Y, Ta, Hf, and/or Si. Electrochemical testing was carried out to determine corrosion rates. The bare In800H and 310SS alloys corroded rapidly (~2500 and 4500 µm/yr, respectively, assuming uniform corrosion). Concentrating solar power plants need containment materials with a lifetime of at least 30 years; thus, these corrosion rates are excessive. Corrosion mitigation approaches are being investigated to obtain degradation on the order of 20 µm/yr or lower. The lowest corrosion rate of 190 µm/yr was obtained for atmospheric plasma spray NiCoCrAlY coatings pre-oxidized in air at 900 °C for 24 h with a heating/cooling rate of 0.5 °C/min. Metallographic characterization of the corroded surfaces showed that the formation of a uniform thin alumina scale before exposure to the molten chloride system considerably reduced the corrosionmore » of the alloy. However, the rates of corrosion determined herein are considerable, highlighting the relevance of testing materials durability in solar power applications.« less
Authors:
ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5500-68444
Journal ID: ISSN 2397-2106
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
npj Materials Degradation
Additional Journal Information:
Journal Volume: 1; Journal Issue: 7; Journal ID: ISSN 2397-2106
Publisher:
Springer
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 47 OTHER INSTRUMENTATION; molten salts; corrosion; chlorides; coatings; alumina; oxidation
OSTI Identifier:
1394112