Protective graphite coating on metallic bipolar plates for PEMFC applications

A new design of metallic bipolar plates with pure graphite coating on metal substrates has been developed. The top layer was a continuous graphite sheet made by the expanded graphite flakes. The pure and layered graphite surface provides high electrical conduction and high chemical inertness in PEMFC environments. Between the graphite sheet and the metal substrate was a binder layer, which mainly consisted of ester resin and conductive fillers. It functions as a binder for the graphite layer and as the second protection layer from acid solution as well. The results from the potentiodynamics tests showed rather low corrosion current densities for our proposed materials, even after soaking tests for over 2000 h. The graphite-coated 316L revealed negative (cathodic) current densities either in the PEMFC cathodic or in the anodic environment for the whole polarization period in the potentiostatic experiments. Thus, the graphite-coated SS316L could potentially be used as a bipolar plate material in the PEM fuel cell applications.