Effect of surface oxidation on nickel aluminide alloy IC221M, as a replacement for separator plates in molten carbonate fuel cell

Corrosion behavior of self-coated Nickel Aluminide IC221M alloys were examined in molten carbonate media with LiNaCO3 eutectic composition, to investigate the possibility of usage in wet-seal area in molten carbonate fuel cell. The desired temperature and time of oxidation process assigned as 1000֯ C and 25 hours respectively. Self-coating process resulted the formation of NiO NiAl2O4 ZrO2 and Al2O3 in order, from the outer interface. Under these compounds, in the substrate interface, an Aluminum depleted zone (ADZ) was observed. Oxide compounds together with this layer, perform as a barrier for alloying elements outward diffusion. After immersion test, more stable compounds such as NiCO3 LiAlO2 and CrO3, Na2CrO4 (formed by Cr diffusion), were observed above the ADZ. Weight-gain rate between the 100 to 215 hours of immersion test were estimated 2*10-5 g. cm-2. hrs-1 with a decreasing trend by time progress; which means that the mentioned stable compounds, provide a suitable corrosion resistance in Base alloy, after formation of required amount.