In Situ and Ex Situ Contact Resistance Measurements of Stainless Steel Bipolar Plates for PEM Fuel Cells

Passivation of stainless steel caused by the formation of an oxide layer on the surface is one of the main concerns when it comes to using stainless steel as bipolar plate material. Interfacial Contact Resistance (ICR) between the bipolar plate and the gas diffusion layer was measured both in situ and ex situ. A method for measuring ICR in situ was developed, and initial results showed that the ICR measured in situ is close to the ICR measured ex situ, for both non-coated and gold coated stainless steel bipolar plates. At a compaction pressure of 205.79 N cm-2, the in situ ICR was found to be close to 50 mΩ cm2 and the ex situ measurement performed on the same plate ex situ was found to be approximately 40 mΩ cm2. The in situ method for ICR measurements enables direct studies of the passivation processes at the bipolar plate interface, while the cell is in operation, under the actual fuel cell conditions.