Corrosion performance of 316 stainless steel and nodular cast iron 600-3 in molten Ca(NO3)2-NaNO3-KNO3 salt

The corrosion effect of Ca(NO3)2-NaNO3-KNO3 on 316 stainless steel (316SS) and nodular cast iron 600-3 (QT-600-3) at 520 degrees C was studied by static corrosion method in argon. After corrosion for 100 h, it was found that there were oxides on the corroded surfaces of the two alloys in XRD spectra. The oxide on the surface of 316SS alloy after corrosion was very thin, and the thickness of Cr depleted layer on the surface of corroded 316SS was only 0.4 mu m. On the other hand, a loose oxide layer with a thickness of about 42 mu m was formed on the surface of QT-600-3 after corrosion, and its main components were Fe2O3 and Fe3O4. The corrosion of Ca(NO3)2-NaNO3- KNO3 salt on QT-600-3 is much greater than that on 316SS. The fundamental reason for the different corrosion performance of the two materials was the different oxide structures formed on the surface of the two alloy materials. The results may be helpful to the selection of structural materials when Ca(NO3)2-NaNO3-KNO3 salt is used as the heat storage medium.

Automated summary

The corrosion effect of Ca(NO3)2-NaNO3-KNO3 on 316 stainless steel and nodular cast iron was studied at 520 degrees C. Oxides were found on the corroded surfaces of both alloys after 100 hours of corrosion. The oxide on the surface of 316 stainless steel was thin, while a loose oxide layer with a greater thickness was formed on the surface of nodular cast iron. The different corrosion performance of the two materials was due to the different oxide structures formed on their surfaces.