CORROSION BEHAVIOR OF FE-NI ALLOYS IN MOLTEN CARBONATES .3. CHANGE OFCORROSION BEHAVIOR WITH MELT COMPOSITION

The immersion test and the A. C. impedance measurements for three Fe-N i alloys (Ni: 5, 9, 15wt%) in Li2CO3-K2CO3 molten salts (Li2CO3/K2CO3 molar ratio: 43/57, 50/50, 62/38) were carried out at 923K and 1atm CO 2 atmosphere to investigate the change of corrosion behavior of the Fe -Ni alloys with the melt composition. The weight of oxide film on the alloy immersed in the melt and the amount of dissolved Fe ion into the melt showed a minimum value in the 50/50 melt. These results indicate d that corrosiveness of the alloy was minimum in the 50/50 melt. As th e results of A. C. impedance analysis for these samples, the anodic re sistance showed a maximum value in the 50/50 melt. Therefore, it was c onsidered that the dimension of maximum resistance made the alloy less corroded in the melt. Such an unusual corrosion behavior in the 50/50 melt could not be explained from the viewpoint of basicity. According to viscosity, equivalent conductivity, and surface tension of the mel t, the microstructural change of the melt with the composition was con sidered to affect the change of corrosion behavior.