Corrosion behavior of Fe based container alloys in molten Na2CO3-K2CO3 as thermal energy storage medium for reversible solid oxide cells

In this work corrosion behavior of SUS 441, Crofer 22 APU and Canthal APM in molten Na2CO3-K2CO3 at 800 degrees C is studied. The 441 and APU corrode heavily as the element Cr in the steel is oxidized to NaCrO2. Cr diffuses along grain boundary preferentially and the molten salt penetrates through the corrosion layer. Several porous corrosion layers rich in Cr, O, Na or rich in Fe are formed alternatively on the APU surface. On the contrary, the APM alloy shows excellent corrosion resistance (0.02 mm/y) due to formation of a protective Al2O3 layer.

Automated summary

The corrosion behavior of SUS 441, Crofer 22 APU, and Canthal APM in molten Na2CO3-K2CO3 at 800 degrees C was studied. The results showed that due to the oxidation of Cr in the steel to NaCrO2, 441 and APU corroded heavily, while the APM alloy exhibited excellent corrosion resistance due to the formation of a protective Al2O3 layer.