An Electrochemical Investigation of Potential Metallic Bipolar Plate Materials for PEM Fuel Cells

Increasing attention is being paid to the use of metallic materials as a replacement for non-porous graphite in bipolar plates (BPs) for polymer exchange membrane (PEM) fuel cells. The ideal BP material should demonstrate high values of electrical conductivity, thermal conductivity, corrosion resistance and compressive strength and low values of hydrogen/gas permeability and density. Although metallic materials demonstrate many of those properties, their corrosion resistance can be inadequate, which in turn can lead to unacceptable values of contact resistivity. In this study the corrosion properties of SS316L, SS347, SS410, Al6061 alloy, A36 steel and Ti were investigated in simulated PEMFC anode and cathode environments. SS316L, SS347 and Ti exhibited better corrosion resistance than the other metals. The three metals had similar anodic and cathodic corrosion current densities; the corrosion current was negative in the simulated anode conditions and positive in the simulated cathode conditions. These negative currents arose because of the reaction 2H(+)+2e(-)-> H-2 on the metal electrode and 2H(2)O -> 4H(+)O(2)+4e(-) on the platinum electrode. This did not cause corrosion of the metal surface because the negative currents provide cathodic protection. For the Al6061 alloy, and the A36 steel, the cathodic corrosion current density was much larger than the anodic current density. However, for SS410, the anodic current density is larger. Although SS316L, SS347 and Ti had the better corrosion resistance, they still corroded and metal ions would migrate to membrane and therefore degrade both the membrane and the fuel cell performance.