Bilayer coating system for an electrically conductive element in a fuel cell
View Patent ↗The present invention relates to an electrically conductive element for an electrochemical cell comprising an electrically conductive corrosion-susceptible metal substrate having a surface susceptible to passivation by forming oxides in the presence of oxygen. The surface is treated to remove any oxides present, and then is overlaid with an electrically conductive corrosion-resistant coating comprising one or more elements from Groups 4, 5, 10 , or 11 of the Periodic Table, and then a corrosion-resistant electrically conductive polymer-based coating. The underlying substrate thus has improved corrosion-resistance while maintaining electrical conductivity. Other preferred aspects of the present invention include methods of treating the electrically conductive contact element to resist corrosion while still maintaining electrical conductivity.
1. A method for treating an electrically conductive element for use in a fuel cell comprising:
providing a conductive corrosion-susceptible metal substrate having a surface susceptible to passivation by forming oxides in the presence of oxygen;
removing said oxides from said surface;
depositing an electrically conductive coating onto said surface, said coating comprising one or more elements selected from Groups 4 , 5 , 10 , or 11 of the Periodic Table, having a thickness of less than about 50 microns; and
applying an electrically conductive corrosion-resistant polymer-based coating overlaying said coating comprising said one or more elements on said surface.
2. The method according to claim 1 , wherein said metal substrate is selected from the group consisting of: aluminum, magnesium, titanium, alloys and mixtures thereof.
3. The method according to claim 1 , wherein said metal substrate comprises aluminum.
4. The method according to claim 1 , wherein said removing is conducted in a vacuum.
5. The method according to claim 1 , wherein said removing is conducted by plasma cleaning.
6. The method according to claim 1 , wherein said one or more elements selected from Groups 4 , 5 , 10 , or 11 is selected from the group consisting of: titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), Tantalum (Ta), Gold (Au), Platinum (Pt) and mixtures and alloys thereof.
7. The method according to claim 1 , wherein said one or more elements are selected from Groups 4 or 5 of the Periodic Table.
8. The method according to claim 1 , wherein said one or more elements of said coating comprises titanium (Ti).
9. The method according to claim 8 , wherein said coating comprising one or more elements comprises a compound selected from the group consisting of: titanium nitride (TiN), titanium suboxide (TiO x , where x<2), and mixtures thereof.
10. The method according to claim 1 , wherein said coating comprising one or more elements comprises one or more layers.
11. The method according to claim 1 , wherein said coating comprising one or more elements has a thickness of between about 0.1 microns to about 50 microns.
12. The method according to claim 1 , wherein said coating comprising one or more elements has a thickness of between about 0.5 microns to about 5 microns.
13. The method according to claim 1 , wherein said applying of said polymer-based coating is conducted by a process selected from the group consisting of: coating, brushing, spraying, spreading, dipping, rolling, laminating, and powder coating.
14. A method according to claim 1 , wherein before said applying, a matrix is formed comprising a polymer and conductive particles, and said matrix is applied to form said polymer-based coating.
15. A method according to claim 1 , wherein said depositing of said coating comprising one or more elements is conducted by ion-assisted physical vapor deposition.
16. A method for treating an electrically conductive element for use in a fuel cell comprising:
providing a conductive corrosion-susceptible metal substrate having a surface susceptible to passivation by forming oxides in the presence of oxygen;
treating said substrate to remove said oxides from said surface;
depositing an electrically conductive corrosion-resistant titanium-based coating comprising titanium (Ti) onto said surface; and
applying an electrically conductive corrosion-resistant polymer-based coating overlaying said titanium-based coating on said surface.
17. The method according to claim 16 , wherein said titanium-based coating comprises suboxides of titanium.
18. The method according to claim 16 , wherein said metal substrate is selected from the group consisting of: aluminum, magnesium, titanium, alloys and mixtures thereof.
19. The method according to claim 16 , wherein said metal substrate comprises aluminum.
20. The method according to claim 16 , wherein said treating is conducted in a vacuum.
21. The method according to claim 16 , wherein said treating is conducted by plasma cleaning.
22. The method according to claim 16 , wherein said titanium-based coating applied by said depositing comprises one or more layers.
23. The method according to claim 16 , wherein said titanium-based coating has a thickness of between about 0.1 microns to about 50 microns.
24. The method according to claim 16 , wherein said titanium-based coating has a thickness of between about 0.5 microns to about 5 microns.
25. The method according to claim 16 , wherein said applying of said polymer-based coating is conducted by a process selected from the group consisting of: coating, brushing, spraying, spreading, dipping, rolling, laminating, and powder coating.
26. A method according to claim 16 , wherein before said applying, a matrix is formed comprising a polymer and conductive particles, and said matrix is applied to form said polymer-based coating.
27. A method according to claim 16 , wherein said depositing of said coating comprising titanium is conducted by ion-assisted physical vapor deposition.
28. An electrically conductive element for use in a fuel cell comprising:
an electrically conductive corrosion-susceptible metal substrate having a surface susceptible to passivation by forming oxides in the presence of oxygen; wherein said surface is substantially free of said oxides and overlaid with an electrically conductive corrosion-resistant coating comprising one or more elements selected from Groups 4 , 5 , 10 , or 11 of the Periodic Table and having a thickness of less than 50 microns; and
a corrosion-resistant electrically conductive polymer-based coating applied over said conductive corrosion-resistant coating on said surface.
29. The electrically conductive element according to claim 28 , wherein said metal substrate is selected from the group consisting of: aluminum, magnesium, titanium, alloys and mixtures thereof.
30. The electrically conductive element according to claim 28 , wherein said metal substrate comprises aluminum.
31. The electrically conductive element according to claim 28 , wherein said corrosion-resistant coating comprising one or more elements comprises one or more layers.
32. The electrically conductive element according to claim 28 , wherein said one or more elements of said coating selected from Groups 4 , 5 , 10 , or 11 is selected from the group consisting of: titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), Tantalum (Ta), Gold (Au), Platinum (Pt) and mixtures and alloys thereof.
33. The electrically conductive element according to claim 28 , wherein said one or more elements of said coating are selected from Groups 4 or 5 of the Periodic Table.
34. The electrically conductive element according to claim 33 , wherein said one or more elements of said coating comprises titanium (Ti).
35. The electrically conductive element according to claim 34 , wherein said coating comprising one or more elements comprises a compound selected from the group consisting of: titanium nitride (TiN), titanium suboxide (TiO x , where x<2), and mixtures thereof.
36. The electrically conductive element according to claim 28 , wherein said corrosion-resistant coating comprising one or more elements has a thickness of between about 0.1 microns to about 50 microns.
37. The electrically conductive element according to claim 28 , wherein said corrosion-resistant coating comprising one or more elements has a thickness of between about 0.5 microns to about 5 microns.
38. The electrically conductive element according to claim 28 , wherein said substrate having said corrosion-resistant coating comprising one or more elements and said polymer-based coating has a contact resistance of less than 50 mOhm-cm 2 under a compressive force of 50 psi (350 kPa) or greater.
39. The electrically conductive element according to claim 38 , wherein said substrate having said corrosion-resistant coating comprising one or more elements and said polymer-based coating has a contact resistance of less than 25 mOhm-cm 2 under a compressive force of 50 psi (350 kPa) or greater.
40. The electrically conductive element according to claim 28 , wherein said polymer-based coating comprises a matrix of a polymeric binder and a plurality of electrically conductive particles.
41. The electrically conductive element according to claim 40 , wherein said electrically conductive particles of said polymer-based coating are selected from the group consisting of: gold, platinum, nickel, tin, silver, palladium, noble metals, graphite, carbon black, and mixtures thereof.
42. The electrically conductive element according to claim 40 , wherein said electrically conductive particles comprise graphite and carbon black.
43. The electrically conductive element according to claim 42 , wherein said graphite is selected from the group consisting of: expanded graphite, graphite powder, graphite flakes, and mixtures thereof.
44. The electrically conductive element according to claim 42 , wherein said total amount of graphite and carbon combined are present in said matrix at less than about 40% by weight.
45. The electrically conductive element according to claim 40 , wherein said polymeric binder is selected from the group consisting of: poly vinyl esters, polyamide-imides, polyimides, polyether-imides, epoxies, silicones, polyphenols, fluoro-elastomers, polyesters, phenoxy-phenolics, epoxide-phenolics, acrylics, urethanes, and mixtures thereof.