Early-stage corrosion of IN 740H alloy in eutectic NaCl-KCl molten salt at high temperatures

Gore, P and Singh, MP and Suryateja, D and Basu, B and Chattopadhyay, K (2023) Early-stage corrosion of IN 740H alloy in eutectic NaCl-KCl molten salt at high temperatures. In: Solar Energy, 252 . pp. 330-341.

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Abstract

The next generation concentrated solar power plants are expected to operate at temperatures above 700 °C and this would necessitate heat storage media such as chloride salt mixtures to be used for better heat transfer and energy storage. In this perspective, the corrosion behaviour of a commercial grade IN 740H alloy is being investigated in the eutectic equimolar NaCl-KCl salt mixture, at 700 °C and 800 °C. To evaluate and understand the early stages of corrosion of IN 740H, electrochemical and gravimetric tests were carried out after exposure to molten eutectic NaCl-KCl salt mixture for 1.5 and 24 h, respectively. The quantitative outcomes of the gravimetric studies suggest that IN 740H corrodes at 0.29 ± 0.03 and 0.59 ± 0.17 mg cm−2 day−1 at 700 °C and 800 °C, respectively. Tafel measurements reveal corrosion rates similar to those measured by gravimetric method. Electrochemical impedance spectroscopy analysis indicated the diffusion-controlled corrosion behaviour, but the passive layer does not inhibit corrosion at early stages. A correlation between the underlying mechanism and the oxide scale microstructure has been presented using electrochemical and cross-sectional studies.

Item Type:	Journal Article
Publication:	Solar Energy
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd.
Keywords:	Concentrated solar power; Electrochemical impedance spectroscopy; IN 740H alloy; Internal oxidation; Molten salts
Department/Centre:	Division of Chemical Sciences > Materials Research Centre Division of Interdisciplinary Sciences > Interdisciplinary Centre for Energy Research Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	25 Feb 2023 07:44
Last Modified:	25 Feb 2023 07:44
URI:	https://eprints.iisc.ac.in/id/eprint/80673

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