Corrosion Behavior of Porous Metal Fiber-Sintered Felt in Both Simulated and Practical Environments of a Direct Methanol Fuel Cell

This study deals with corrosion behaviors of the porous metal fiber-sintered felt (PMFSF), which is intended to be used as the anodic methanol barrier in a passive air-breathing direct methanol fuel cell (PAB-DMFC) so as to reduce methanol crossover. Among the tested materials, the AISI 316L (UNS S31603) stainless steel exhibits higher performances than the pure copper, Cu-Be/Cu-Be-Ni alloys, and Ni-coated copper in the simulated DMFC environment, because a relatively stable passive film can be formed on its surface at a passive current density between 10−6 A cm−2 and 10−5 A cm−2. The morphology features further showed that the AISI 316L in the simulated anode environment suffers more from both intergranular corrosion and pitting corrosion than the cathode environment. When a Cu-based PMFSF is used in the practical environment of a PAB-DMFC, evident corrosion behaviors can be observed as a result of copper oxidation. Results suggest that corrosion cracks are formed on the surface of copper fibers, and the corrosion products contain both copper oxide (CuO) and cuprous oxide (Cu2O). In contrast, the AISI 316L stainless steel exhibits acceptable performance in the practical operation so that it can be treated as a candidate to make the PMFSF for practical DMFC applications.