Aluminum Bipolar Plates for PEM Fuel Cells

Aluminum is an attractive material for fuel cell bipolar plates because it is lightweight, and relatively easy to form with features for flow channels and to weld. The challenge is that it is highly susceptive to corrosion in fuel cell operation environment. For instance if the aluminum contacts the highly cathodic carbon in the gas diffusion layers, it can be come a sacrificial anode.  Al will also oxidize at the low pH of PEM fuel cells, as it is only stable between pH 6-8.    Any aluminum oxide formation on the surface will increase its interfacial contact resistance and result in resistive losses in the stack.    Our approach is to develop a robust coating/protection system for the aluminum, with the final coating consisting of a passivation layer embedded with Au microdots.  The passivation layer prevents the aluminum corrosion while the Au maintains conductivity.  The corrosion of the aluminum is monitored with electrochemical impedance spectroscopy and scanning electron microscopy.    The results are compared to corrosion of titanium and stainless steel bipolar plates with a similar TiO₂/Au coating.