Corrosion Behavior of NiCrMoNb and NiCoFeCrMoNb Alloys in Molten NaCl-KCl-MgCl2 at 700 ℃

doi:10.11902/1005.4537.2025.176

Journal of Chinese Society for Corrosion and protection

2026, Vol. 46

Issue (3): 730-742 DOI: 10.11902/1005.4537.2025.176

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Corrosion Behavior of NiCrMoNb and NiCoFeCrMoNb Alloys in Molten NaCl-KCl-MgCl₂ at 700 ℃

LU Huayi, LI Ruoyu, CHENG Yufei, BAI Yingxiong, WANG Yanli(

)

Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China

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LU Huayi, LI Ruoyu, CHENG Yufei, BAI Yingxiong, WANG Yanli. Corrosion Behavior of NiCrMoNb and NiCoFeCrMoNb Alloys in Molten NaCl-KCl-MgCl₂ at 700 ℃. Journal of Chinese Society for Corrosion and protection, 2026, 46(3): 730-742.

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Abstract

In this study, ingots of NiCrMoNb and NiCoFeCrMoNb alloys were melted and cast using vacuum arc melting method. Then the corrosion behavior and mechanism of these two alloys in molten chloride salts (24.5NaCl-20.55KCl-54.95MgCl₂ (in mass fraction)) in an argon atmosphere at 700 ℃ were comparatively investigated. Results show that the two alloys suffered from significant mass loss in the molten salts. Due to the high oxygen partial pressure in the environment in the initial corrosion stage, scales of discontinuous oxides (including MgNiO₂, MgCr₂O₄, MgNb₂O₆, and Mg₄Nb₂O₉) are formed on the surface of both alloys. In the middle corrosion stage, a continuous and thick MgO scale is developed, which can partially mitigate the corrosion process. In the late corrosion stage, chloride-induced reactions lead to pronounced active dissolution of the alloys, resulting in substantial mass loss. Additionally, the introduction of Co and Fe into the NiCrMoNb alloy results in the coexistence of phases rich in Nb/Mo- and/or in Fe/Co/Ni/Cr within the alloy, which further induce galvanic corrosion. During the entire corrosion process of 200 h, the corrosion behavior of the NiCrMoNb alloy gradually transforms from being controlled by the diffusion rate of charged particles within the oxide scale to being dominated by the diffusion rate of charged particles in the molten salts. In contrast, the corrosion behavior of the NiCoFeCrMoNb alloy remains relatively stable, with its corrosion rate consistently governed solely by the diffusion kinetics of charged particles within the oxide scale throughout the entire corrosion period.

Key words: NiCrMoNb alloy NiCoFeCrMoNb alloy molten chloride salt molten salt corrosion electrochemistry

Received: 09 June 2025 32134.14.1005.4537.2025.176

ZTFLH:

TK51

Fund: Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology(2024K003);Innovation Project of Guangxi Graduate Education(YCSW2025104)

Corresponding Authors: WANG Yanli, E-mail: wyl187358@gxu.edu.cn

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	LU Huayi
	LI Ruoyu
	CHENG Yufei
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	WANG Yanli

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https://www.jcscp.org/EN/10.11902/1005.4537.2025.176 OR https://www.jcscp.org/EN/Y2026/V46/I3/730

Fig.1 Schematic diagram of the melting salt corrosion experiment apparatus

Fig.2 Corrosion kinetics curves of NiCrMoNb and NiCoFeCrMoNb alloys in molten NaCl-KCl-MgCl₂ at 700 ℃

Fig.3 Surface morphologies and corresponding EDS element mappings of NiCrMoNb alloy

Fig.4 Surface morphologies and corresponding EDS element mappings of NiCoFeCrMoNb alloy

Fig.5 XRD patterns of NiCrMoNb alloy immersed in molten NaCl-KCl-MgCl₂ for 25 h (a), 50 h (b), 100 h (c), 150 h (d) and 200 h (e) under 700 ℃ Ar atmosphere

Fig.6 Cross-sectional morphologies and mapping scanning results of NiCrMoNb alloy after immersion in molten NaCl-KCl-MgCl₂ at 700 ℃ under Ar atmosphere for 25 h (a), 50 h (b), 100 h (c), 150 h (d) and 200 h (e)

Fig.7 XRD patterns of NiCoFeCrMoNb alloy immersed in molten NaCl-KCl-MgCl₂ for 25 h (a), 50 h (b), 100 h (c), 150 h (d) and 200 h (e) under 700 ℃ Ar atmosphere

Fig.8 Cross-sectional morphologies of NiCoFeCrMoNb alloy after immersion in molten NaCl-KCl-MgCl₂ at 700 ℃ under Ar atmosphere for 25 h (a), 50 h (b), 100 h (c), 150 h (d) and 200 h (e)

Fig.9 Nyquist (a) and Bode (b) plots for NiCrMoNb alloy in molten NaCl-KCl-MgCl₂ at 700 ℃ under Ar atmosphere

Fig.10 Nyquist (a) and Bode (b) plots for NiCoFeCrMoNb alloy in molten NaCl-KCl-MgCl₂ at 700 ℃ under Ar atmosphere

Fig.11 Equivalent circuits for EIS data of NiCrMoNb (a, b) and NiCoFeCrMoNb alloys (c) in molten NaCl-KCl-MgCl₂ under Ar atmosphere at 700 ℃

Table 1 Fitting results for EIS data of NiCrMoNb alloy in molten NaCl-KCl-MgCl₂ at 700 ℃

Table 2 Fitting results for EIS data of NiCoFeCrMoNb alloy in molten NaCl-KCl-MgCl₂ at 700 ℃

Fig.12 Corrosion mechanism diagram of NiCrMoNb alloy in molten NaCl-KCl-MgCl₂ at 700 ℃

Fig.13 Corrosion mechanism diagram of NiCoFeCrMoNb alloy in molten NaCl-KCl-MgCl₂ at 700 ℃

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