Adhesive bonds for metalic bipolar plates

An electrically conductive contact element for a PEM fuel cell, said element comprising:

• a first sheet having a first contact surface overlaid with an electrically conductive adhesive primer coating;
• a second sheet having a second contact surface overlaid with said electrically conductive adhesive primer coating;
• one of more bond regions joining said first contact surface and said second contact surface;
• said bond regions having an electrical resistance of less than 5 mOhms-cm2 after 500 hours of operation in fuel cell operating conditions.

An electrically conductive contact element comprising:

• a first sheet having a first contact surface overlaid with an electrically conductive adhesive primer coating;
• a second sheet having a second contact surface overlaid with said electrically conductive adhesive primer coating;
• an electrically conductive adhesive disposed between said first contact surface and said second contact surface in electrical contact regions;
• and
• wherein said electrically conductive adhesive primer coating comprises graphite, carbon black, and a polymeric binder and said total amount of graphite and carbon combined are present in said matrix at less than about ten percent by weight.

A fuel cell stack comprising a plurality of fuel cells and an electrically conductive element sandwiched between an anode and cathode of adjacent fuel cells comprising:

• a first electrically conductive sheet having an anode confronting surface and a first heat exchange surface;
• a second electrically conductive sheet having a cathode confronting surface and a second heat exchange surface;
• wherein said first and second heat exchange surfaces are coated with a primer coating comprising a first plurality of electrically conductive particles dispersed in a corrosion resistant polymer;
• said first and second heat exchange surfaces confronting each other so as to define therebetween a coolant flow passage adapted to receive a liquid coolant and being electrically coupled to one another at a plurality of sites via an electrically conductive adhesive, said electrically conductive adhesive comprising a second plurality of conductive particles dispersed in a polymer having adhesive properties;
• and
• wherein said primer coating and said electrically conductive adhesive together define an electrically conductive path between said first and second sheets.

A method of increasing bond durability of an electrically conductive element in a fuel cell, the method comprising:

• coating a first surface of a first sheet and a second surface of a second sheet with an electrically conductive adhesive primer;
• disposing an electrically conductive adhesive between said first and second coated surfaces;
• thereby joining said first and said second coated surfaces together;
• wherein said adhesive is selected for sustained sealing engagement with the adhesive primer applied on said first and said second surfaces.