Ryuichiro Ebara1, Hiroshi Nakajima1, Daisaku Shouzen1 and Tamotsu Yamada1
1Hiroshima R&D Center, Mitsubishi Heavy Industries, Ltd., Hiroshima
Molten salt corrosion behaviour of heat transfer plant materials, SS41, 2\frac14Cr-1Mo Steel, SUS304 and Inconel 625, was studied in a molten salt environment of (50%KNO3 and 50%NaNO3) at temperatures of 450 and 550°C.
The corrosion rate in the molten salt decreased in the decreasing order of SS41, 2\frac14Cr-1Mo Steel, SUS304, Inconel 625. And the corrosion resistance of SS41, 2\frac14Cr-1Mo Steel and SUS304 strongly depended on the temperature and Cl- content of the molten salt, while Inconel 625 showed high corrosion resistance in the molten salt environment.
The morphology of corrosion products were examined by electron probe microanalysis (EPMA), X-ray diffraction, scanning electron microscopy (SEM) and auger electron spectroscopy (AES). Corrosion products of SS41 and 2\frac14Cr-1Mo Steel consisted of porous and easy-pearling multilayer films of α -Fe2O3, KFeO2, NO2O-Fe2O3, and Fe3O4. While, the corrosion products of SUS304 and Inconel 625 consisted of compact and well-sticked iron oxide films which contain Ni and Cr.
The materials containing much more than 10 wt%Cr showed high corrosion resistance against the molten salt.
molten salt corrosion, statistics of extremes, Inconel 625, chromium-molybdenum steel, Auger electron spectroscopy, oxide scale
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