Resistivity of bipolar plate materials at the cathode interface in molten carbonate fuel cells.

摘要

Measurements of oxide scale resistivity for prospective bipolar plate materials in the molten carbonate fuel cell (MCFC) are coupled with observations of microstructural/compositional change over time. This work searches for a compromise to the high corrosion rate of Type 316L and the high oxide scale resistance of Type 310S. We tested a group of materials having chromium content ranging from 16 to 31 wt%, including Nitronic 50 and NKK, a Ni-Cr-Fe alloy. Chromium content was found to be the primary determinant of oxide scale composition. In the MCFC cathode compartment, stainless steels generally formed a duplex structure with an inner Cr-rich layer and an outer, Fe-rich layer. The composition of the inner Cr-rich layer was related to the base alloy and had a controlling effect on scale resistivity. Oxide scale resistivity was measured for two electrolyte compositions: Li/K and Li/Na carbonates. Changes in the physical/mechanical properties (spallation/cracking) in the oxide scale of Type 316L provided an understanding of its resistivity fluctuations over time.