(Invited) Coatings for Robust Metal Bipolar Plates

Metal bipolar plates have advantages of lighter weight and smaller volume over graphite based bipolar plates for automobile fuel cell stacks.  Stainless steel has been identified as the primary candidate of the substrate.  It has reasonable corrosion resistant, high electrical and thermal conductivity, suitable mechanical properties and formability to form the proper flow field by conventional high speed stamping process.  The most important, SS foil is widely commercially available and used in various markets, which result in its low cost comparing with other corrosion resistant alloys. 

Additional treatment on stainless steel is necessary for three reasons.  First is to reduce the surface electrical contact resistance with gas diffusion layer.  The second is to further improve the corrosion resistance of stainless steel in PEM fuel cell stack operation conditions, especially under the transient high voltage conditions.  The third is to minimize the absorption of leached ions on the electrode catalyst that may poison electrodes.

Two types of coatings have been investigated.  One is the coating using precious metal, the other is precious metal free coating technologies.  The advantages and progresses of each coating will be reviewed. 

TreadStone has been involved in corrosion resistant metal plate development for several years.  A unique design of metal plate coating and its low cost fabrication technology have been developed.  It has demonstrated stable long term (2,000 hours) operation for automobile fuel cell stacks under dynamic operation conditions.  More development activites are on-going to further reduce the cost with the supports from US Department of Energy.