The corrosion mechanism of Fe-based superalloy in molten NaCl-52 wt-%MgCl 2 at 520°C

Abstract

NaCl-52 wt-%MgCl₂ is a good thermal storage medium at medium–high temperature. But the corrosion of chlorate on metal is serious and the mechanism is unclear. In this paper, the corrosion kinetics curves of Fe and three kinds of Fe-based superalloys were measured by the immersion salt corrosion method at 520°C. The microstructure and composition on the surface and cross-section were characterised by a scanning electron microscopy with EDS analysis and X-ray diffraction. The results show that corrosion kinetics curves obey linear law, and the average mass loss rate of Fe is the lowest of all. After corrosion for 20 h, the main composition on Fe surface was mainly magnesia (MgO) and Fe. Shell structure appeared on the surface of three alloys, the composition of shell was MgO, while matrix had Fe, Ni and its compounds. After corrosion for 160 h, the surfaces of four samples became loose, and they generated different corrosion products. The cross-sectional morphology and line scanning analysis results show that Fe corrosion is relatively mild, while Fe-based alloys presented obvious corrosion layer, and the content of Fe and Cr near corrosion layer decreased. The corrosion mechanism of Fe-based superalloys mainly involves oxidation–chlorination.

Keywords

Corrosion superalloy molten salt corrosion mechanism

Get full access to this article

View all access options for this article.

References

Robe

Säck

J-P

Rietbrock

. Test operation of a 100 kW pilot plant for solar hydrogen production from water on a solar tower. Sol Energ. 2011; 85 (4): 634–644. doi: 10.1016/j.solener.2010.04.014

Wang

. Modeling and simulation of 1 MW DAHAN solar thermal power tower plant. Renew Energy. 2011; 36 (2): 848–857. doi: 10.1016/j.renene.2010.08.010

Gil

Medrano

Martorell

. State of the art on high temperature thermal energy storage for power generation. Part 1 – concepts, materials and modellization. Renew Sustain Energy Rev. 2010; 14 (1): 31–55. doi: 10.1016/j.rser.2009.07.035

Herrmann

Kearney

. Survey of thermal energy storage for parabolic trough power plants. J Sol Energy Eng. 2002; 124 (2): 145–152. doi: 10.1115/1.1467601

Kenisarin

. High-temperature phase change materials for thermal energy storage. Renew Sustain Energy Rev. 2010; 14 (3): 955–970. doi: 10.1016/j.rser.2009.11.011

Liu

Zeng

. Corrosion behavior of three stainless steels in molten LiCl-5% Li2O at 700°C. Corros Sci Protect Technol. 2012; 24 (2): 113–116. Chinese.

Zhou

. Exploitation and comprehensive utilization for Qinghai salt lakes. Prog Chem. 2013; 25 (10): 1613–1624. Chinese.

Ishitsuka

Nose

. Stability of protective oxide films in waste incineration environment-solubility measurement of oxides in molten chlorides. Corros Sci. 2002; 44 (2): 247–263. doi: 10.1016/S0010-938X(01)00059-2

Ishitsuka

Nose

. Solubility study on protective oxide films in molten chlorides created by refuse incineration environment. Mater Corros. 1999; 51 (3): 177–181. doi: 10.1002/(SICI)1521-4176(200003)51:3<177::AID-MACO177>3.0.CO;2-O

10.

Shores

Mohanty

. Role of chlorides in hot corrosion of a cast Fe–Cr–Ni alloy. Part II: thermochemical model studies. Corros Sci. 2004; 46 (12): 2909–2924. doi: 10.1016/j.corsci.2004.04.014

11.

Sun

. Experimental research on molten salt corrosion property and optimization. Beijing: Beijing University; 2007, p. 1–55. Chinese.

12.

Rahman

Castro

. Environmental impacts of electricity generation: a global perspective. IEEE Trans Energy Convers. 1995; 10 (2): 307–314. doi: 10.1109/60.391897

13.

. High temperature corrosion of metallic materials inducted by chloride salts [Doctoral dissertation]. Da Lian: Da Lian University of Technology; 2003, p. 1-115. Chinese.

14.

Zahs

Spiegel

Grabke

. Chloridation and oxidation of iron, chromium, nickel and their alloys in chloridizing and oxidizing atmospheres at 400-700°C. Corros Sci. 2000; 42 (6): 1093–1122. doi: 10.1016/S0010-938X(99)00142-0

15.

Cho

Zhang

. Corrosion behavior and effect of alloying elements of Fe-base and Ni-base superalloys on hot molten salt. Korean J Mater Res. 1999; 9 (10): 985.

16.

Omary

Niu

. The corrosion of various materials under chloride deposits at 623-723 K in pure oxygen: high temperature materials and processes. High Temp Mat Process. 2002; 21 (1-2): 11–24.