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Journal of Chinese Society for Corrosion and protection  2021, Vol. 41 Issue (1): 80-86    DOI: 10.11902/1005.4537.2020.012
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Effect of Mg on Corrosion of 316H Stainless Steel in Molten Salts MgCl2-NaCl-KCl
ZUO Yong1,2,3(), CAO Mingpeng1,3, SHEN Miao1,2, YANG Xinmei1,2,3
1.Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
2.Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian 116023, China
3.University of Chinese Academy of Sciences, Beijing 100049, China
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Abstract  

The effect of Mg on purification of molten salts MgCl2-NaCl-KCl (MNKC) and corrosion behavior of 316H stainless steel in MNKC molten salts were investigated by means of immersion test and electrochemical means. Results indicated that the corrosion of 316H stainless steel in MNKC molten salts at 600 ℃ was well inhibited when the addition amount of Mg exceeds 500 μg·g-1, correspondingly, 316H stainless steel presents the free corrosion potential of Ecorr<-0.80 V vs NiCl2/Ni, corrosion current density of Icorr<25 μA/cm2, and linear polarization resistance of Rp>800 Ω·cm2. The purification and corrosion inhibition mechanism of Mg for the MNKC molten salts were discussed simultaneously.

Key words:  chloride molten salt      corrosion mitigation      316H stainless steel      concentrated solar power (CSP)     
Received:  17 January 2020     
ZTFLH:  TG174  
Fund: Strategic Priority Research Program of Chinese Academy of Sciences(XDA21000000)
Corresponding Authors:  ZUO Yong     E-mail:  zuoyong@sinap.ac.cn

Cite this article: 

ZUO Yong, CAO Mingpeng, SHEN Miao, YANG Xinmei. Effect of Mg on Corrosion of 316H Stainless Steel in Molten Salts MgCl2-NaCl-KCl. Journal of Chinese Society for Corrosion and protection, 2021, 41(1): 80-86.

URL: 

https://www.jcscp.org/EN/10.11902/1005.4537.2020.012     OR     https://www.jcscp.org/EN/Y2021/V41/I1/80

Fig.1  Cyclic voltammetric curves of MNKC molten salt on a tungsten electrode at 600 ℃ with a scan rate of 0.1 V/s
Fig.2  Dependence of the corrosion potential of the 316H stainless steel on the amount of magnesium added into the MNKC molten salt at 600 ℃
Fig.3  Polarization curves of the 316H stainless steel in MNKC-Mg (0~1200 μg·g-1) system
Fig.4  Dependence of the corrosion current density of the 316H stainless steel on the amount of magnesium added into the MNKC molten salt at 600 ℃
Fig.5  Dependence of the linear polarization resistance of the 316H stainless steel on the amount of magnesium added into the MNKC molten salt at 600 ℃
Fig.6  Cyclic voltammetric curves of MNKC-0.2%CrCl2 molten salt on a tungsten electrode at 600 ℃ with a scan rate of 0.1 V/s
PeakStart point / VEnd point / VCorresponding reaction
A1-0.80-0.75

2Cr+O2--4e→Cr2O2+

Cr+O2--2e→CrO

A2-0.71-0.62Cr-2e→Cr2+
A3-0.58-0.49

2Cr2++3O2--2e→Cr2O3

Cr2O2++2O2--2e→Cr2O3

2CrO+O2--2e→Cr2O3

A4-0.46-0.43Cr2+-e→Cr3+
C1-0.80-0.87

Cr2O2++4e→2Cr+O2-

CrO+2e→Cr+O2-

C2-0.75-0.81Cr2++2e→Cr
C3-0.56-0.63

Cr2O3+2e→2Cr2++3O2-

Cr2O3+2e→Cr2O2++2O2-

Cr2O3+2e→2CrO+O2-

Table 1  Assignment of redox peaks in the cyclic voltammetry curve
Fig.7  Cross-sectional SEM image of the 316H stainless steel exposed in molten MNKC-500 μg·g-1 Mg under Ar atmosphere at 600 °C for 100 h
Fig.8  Cross-sectional SEM image of the 316H stainless steel exposed in molten MNKC without Mg under Ar atmosphere at 600 °C for 100 h
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