Corrosion resistance of alumina-forming alloys against molten chlorides for energy production. I: Pre-oxidation treatment and isothermal corrosion tests

Journal Article · Fri Feb 24 00:00:00 EST 2017 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2017.02.019· OSTI ID:1353426

Gomez-Vidal, J. C. ^[1]; Fernandez, A. G. ^[2]; Tirawat, R. ^[1]; Turchi, C. ^[1]; Huddleston, W. ^[1]

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1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Antofagasta, Antofagasta (Chile)

Advanced components in next-generation concentrating solar power (CSP) applications will require advanced heat-transfer fluids and thermal-storage materials that work from about 550 °C to at least 720 °C, for integration with advanced power-conversion systems. To reach the cost target, less-expensive salts such as molten chlorides have been identified as high-temperature fluid candidates. High-strength alloys need to be identified and their mechanical and chemical degradation must be minimized to be used in CSP applications. Approaches for corrosion mitigation need to be investigated and optimized to drive down corrosion rates to acceptable levels—in the order of tens of micrometers per year—for achieving a long system lifetime of at least 30 years. Surface passivation is a good corrosion mitigation approach because the alloy could then be exposed to both the liquid and the vapor phases of the salt mixture. In this investigation, we pre-oxidized the alumina-forming alloys Inconel 702, Haynes 224, and Kanthal APMT at different temperatures, dwelling times, and atmospheres to produce the passivation by forming protective oxides at the surface. The pretreated alloys were later corroded in molten MgCl2 – 64.41 wt% KCl at 700 °C in a flowing Ar atmosphere. We performed electrochemical techniques such as open-circuit potential followed by a potentiodynamic polarization sweep and conventional long-term weight-change tests to down-select the best-performing alloy and pre-oxidation conditions. The best corrosion results were obtained for In702 pre-oxidized in zero air at 1050 °C for 4 h. Finally, metallographic characterization of the pre-oxidized alloys and of the corroded surfaces showed that the formation of dense and uniform alumina scale during the pre-oxidation appears to protect the alloy from attack by molten chloride.

• Research Organization: NREL (National Renewable Energy Laboratory (NREL), Golden, CO (United States))
• Sponsoring Organization: USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1353426
• Alternate ID(s): OSTI ID: 1396893
• Report Number(s): NREL/JA--5500-66778
• Journal Information: Solar Energy Materials and Solar Cells, Journal Name: Solar Energy Materials and Solar Cells Journal Issue: C Vol. 166; ISSN 0927-0248
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
alumina
alumina forming alloys
chlorides
corrosion
molten salts
oxidation