Fuel cell flow field having strong, chemically stable metal bipolar plates

1. A device for use in a fuel cell stack, comprising:

a bipolar plate having at least one first metal layer that is solid and continuous, the at least one first metal layer including a cathode side and an anode side that each include reactant gas channels, and having a first oxide layer with a first growth rate in the presence of a fuel cell reactant gas; and

a plurality of second metal layers, with one of the plurality of second metal layers being directly adjacent to the anode side and another of the plurality of second metal layers being directly adjacent the cathode side, each of the plurality of second metal layers comprising a mesh having a second oxide layer with a second growth rate less than the first growth rate in the presence of the fuel cell reactant gas such that the second oxide layer maintains a selected electrical conductivity, each of the plurality of second metal layers being directly bonded to the at least one first metal layer for providing an electrically conductive path between an electrode and the at least one first metal layer.

2. The bipolar plate as recited in claim 1 , wherein the mesh comprises a planar sheet in direct contact with the at least one first metal layer and extending over the reactant gas channels.

3. The bipolar plate as recited in claim 1 , wherein each of the plurality of second metal layers comprises a nickel or nickel alloy, titanium or titanium alloy, stainless steel, platinum or platinum alloy, or combination thereof.

4. The bipolar plate as recited in claim 1 , wherein each of the plurality of second metal layers comprises a nickel alloy.

5. The bipolar plate as recited in claim 4 , wherein the nickel alloy includes a nominal composition of about 22 wt % chromium, about 14 wt % tungsten, about 2 wt % molybdenum, about 0.5 wt % manganese, about 0.4 wt % silicon, about 0.3 wt % aluminum, about 0.10 wt % carbon, about 0.02 wt % lanthanum, up to about 5 wt % cobalt, up to about 3 wt % iron, up to about 0.015 wt % boron, and a remainder wt % nickel.

6. The bipolar plate as recited in claim 1 , wherein the at least one first metal layer comprises steel.

7. The bipolar plate as recited in claim 1 , wherein:

the at least one first metal layer comprises steel; and

each of the plurality of second metal layers includes a nominal composition of about 22 wt % chromium, about 14 wt % tungsten, about 2 wt % molybdenum, about 0.5 wt % manganese, about 0.4 wt % silicon, about 0.3 wt % aluminum, about 0.10 wt % carbon, about 0.02 wt % lanthanum, up to about 5 wt % cobalt, up to about 3 wt % iron, up to about 0.015 wt % boron, and a remainder wt % nickel.

8. The bipolar plate as recited in claim 1 , wherein the at least one first metal layer comprises a first corrosion resistance corresponding to the first growth rate and the at least one second metal layer comprises a second corrosion resistance corresponding to the second growth rate.

9. A fuel cell assembly comprising:

a plurality of electrodes; and

a bipolar plate associated with the electrodes, the bipolar plate comprising:

at least one first metal layer that is solid and continuous, the at least one first metal layer including a cathode side and an anode side that each include reactant gas channels, and having ability to grow an oxide layer with a first growth rate in the presence of a fuel cell reactant gas; and

a plurality of second metal layers, with one of the plurality of second metal layers being directly adjacent to the anode side and another of the plurality of second metal layers being directly adjacent the cathode side, the plurality of second metal layers each comprising a mesh having ability to grow a second oxide layer with a second growth rate in the presence of the fuel cell reactant gas such that the second oxide layer maintains a selected electrical conductivity, each of the plurality of second metal layers being directly bonded to the at least one first metal layer for providing an electrically conductive path between one of the plurality of electrodes and the at least one first metal layer.

10. The assembly as recited in claim 9 , wherein the mesh of each of the plurality of second metal layers includes wires defining openings there between.

11. The assembly as recited in claim 9 , further including a polymer exchange membrane arranged between two of the plurality of electrodes.

12. The assembly as recited in claim 9 , wherein the at least one first metal layer has a uniform thickness.

13. The assembly as recited in claim 9 , wherein each of the plurality of second metal layers is bonded to the at least one first metal layer.

14. The assembly as recited in claim 9 , wherein each of the plurality of second metal layers comprises a nickel alloy and the at least one first metal layer comprises steel.

15. The assembly as recited in claim 9 , wherein each of the plurality of second metal layers is in direct contact with the one of the electrodes on one side and in direct contact with the at least one first metal layer on an opposite side.

16. A method of using a bipolar plate, the method comprising:

providing a bipolar plate having at least one first metal layer that is solid and continuous, the at least one first metal layer including a cathode side and an anode side that each include reactant gas channels, and having a first oxide layer with a first growth rate in the presence of a fuel cell reactant gas and a plurality of second metal layers, with one of the plurality of second metal layers being directly adjacent to the anode side and another of the plurality of second metal layers being directly adjacent the cathode side, each of the plurality of second metal layers comprising a mesh having a second oxide layer with a second growth rate less than the first growth rate in the presence of the fuel cell reactant gas, each of the plurality of second metal layers being directly bonded to the at least one first metal layer for providing an electrically conductive path between an electrode and the at least one first metal layer; and

establishing a resistance to growth of the second oxide layer of the plurality of second metal layers by selecting the at least one first metal layer to include steel and selecting the plurality of second metal layers to include a nickel alloy in order to maintain a selected electrical conductivity in the plurality of second metal layers such that the plurality of second metal layers provide an electrically conductive path between a fuel cell electrode and the at least one first metal layer.