Method of depositing durable thin gold coating on fuel cell bipolar plates
A method of depositing a thin gold coating on bipolar plate substrates for use in fuel cells includes depositing a gold coating onto at least one surface of the bipolar plate substrate followed by annealing the gold coating at a temperature between about 200° C. to 500° C. The annealed gold coating has a reduced porosity in comparison with a coating which has not been annealed, and provides improved corrosion resistance to the underlying metal comprising the bipolar plate.
1. A method of depositing a gold coating onto a bipolar plate for a fuel cell comprising:
providing a bipolar plate substrate having first and second surfaces;
depositing a gold coating onto at least one surface of said substrate; wherein said coating consists essentially of gold nanoparticles; and
annealing said gold coating on said substrate; wherein said annealed gold coating has a reduced porosity in comparison with said gold coating prior to annealing.
2. The method of claim 1 wherein said gold coating comprises nanoparticles having a particle size of about 1 to 12 nm.
3. The method of claim 1 wherein said bipolar plate substrate comprises stainless steel.
4. The method of claim 1 wherein said gold coating is annealed at a temperature between about 200° C. to 500° C.
5. The method of claim 1 wherein said gold coating is annealed at a temperature between about 250° C. to 300° C.
6. The method of claim 3 wherein said gold coating forms an alloy with said stainless steel at annealing temperatures ≧500° C.
7. The method of claim 1 wherein said coating is annealed in a dry, oxygen-free atmosphere.
8. The method of claim 1 wherein said coating is annealed in the presence of hydrogen or an inert gas.
9. The method of claim 8 wherein said coating is annealed in the presence of argon.
10. The method of claim 1 wherein said annealed gold coating has a thickness between about 3 nm and 10 nm.
11. The method of claim 1 wherein said annealed gold coating comprises nanoparticles having a particle size of about 15 to 30 nm.
12. The method of claim 1 wherein said annealed gold coating on said bipolar plate substrate exhibits a contact resistance of about 15 to about 22 mΩ-cm 2 at an applied compression of 200 psi and current density of 1 A/cm 2 .
13. The method of claim 1 wherein said annealed gold coating has a porosity less than about 1% by volume.
14. The method of claim 1 wherein said annealed gold coating exhibits a reduced lattice parameter in comparison with said gold coating prior to annealing.
15. A bipolar plate for use in a fuel cell, said bipolar plate including an annealed gold coating thereon consisting essentially of gold nanoparticles and having a porosity of less than about 1% by volume.
16. The bipolar plate of claim 15 wherein said annealed gold coating exhibits a contact resistance of about 15 to about 22 mΩ-cm 2 at an applied compression of 200 psi and current density of 1 A/cm 2 .
17. The bipolar plate of claim 15 comprising stainless steel.