Coatings for Robust Metal Bipolar Plates

Metal bipolar plates have the advantage of lighter weight and smaller volume over graphite based bipolar plates for automobile PEM fuel cell stacks. Stainless steel has been identified as the primary candidate of the substrate material. It has reasonable corrosion resistance, high electrical and thermal conductivities, suitable mechanical properties, but still needs a surface coating to reduce surface electrical contact resistance and minimize metal ions leached from stainless steel substrate for long term durable operation of PEM fuel cell stacks. Various coating technologies have been investigated to protect stainless steel for PEM fuel cell applications. The coatings using precious metals have the advantage of reliable long term durability because of the exceptional stability of precious metals. The focus of this type of coating is to reduce precious metal usage on metal plate surface. One way to reduce precious metal usage is to deposit precious metal in the form of small dots that only cover a small portion of metal plate surface. It can effective reduce metal bipolar plate cost and meet the application requirement for PEM fuel cells