초록 ▼

The present invention provides an electrically conductive element for a proton exchange membrane fuel cell having low electrical contact resistance and high corrosion resistance. The conductive element comprises a corrosion susceptible metal substrate with a surface, which is preferably treated to a

The present invention provides an electrically conductive element for a proton exchange membrane fuel cell having low electrical contact resistance and high corrosion resistance. The conductive element comprises a corrosion susceptible metal substrate with a surface, which is preferably treated to activate the surface (i.e. to remove a passivation layer of oxides from the surface) with an acidic treatment solution. The treated surface is then overlaid with an electrically conductive, corrosion-resistant, protective coating to protect the substrate re-forming a passivation layer while exposed to the corrosive environment of the fuel cell. The present invention also provides methods of preparing an electrically conductive element to have low electrical contact resistance and high corrosion resistance.

대표청구항 ▼

What is claimed is: 1. A method of treating a surface of a stainless steel substrate having metal oxide at the surface, the method comprising: contacting the surface of the stainless steel substrate with an acidic solution having a pH of from 0 to about 4 comprising one or more halogen ions present

What is claimed is: 1. A method of treating a surface of a stainless steel substrate having metal oxide at the surface, the method comprising: contacting the surface of the stainless steel substrate with an acidic solution having a pH of from 0 to about 4 comprising one or more halogen ions present in said solution at a concentration of less than about 1×10−3 to about 1×10−6 molarity, wherein said solution reacts with the metal oxide in the absence of an impressed electrical current, and said anion reacts with said metal oxide to form a metal halide species soluble in said solution; and separating said metal halide species and said acidic solution from the surface to reduce the amount of said metal oxide thereon, wherein said stainless steel substrate is an electrically conductive element adapted for use in an electrochemical cell, wherein said separating to remove said metal oxide reduces electrical resistance of the surface thereby improving electrical conductivity of the element in said electrochemical cell. 2. The method of claim 1, wherein said contacting is conducted at a temperature of from about 25° C. to about 100° C. 3. The method of claim 1, wherein said contacting is conducted for a duration of less than 600 seconds. 4. The method of claim 1, wherein said separating comprises rinsing the surface with a rinse solution, thereby removing said acidic solution and said metal halide from the surface. 5. The method of claim 1, wherein said solution comprises one or more of water, hydrofluoric acid, sulfuric acid, and nitric acid. 6. The method of claim 1, wherein said solution has a pH of from about 2 to about 4, wherein said solution comprises said one or more halogen ions at a concentration of from about 1×10−3 to about 1×10−5 molarity. 7. The method of claim 1, wherein said metal oxide provides the source of said metal in said metal halide and said halogen ion provides the source of said halide in said metal halide species. 8. The method of claim 1, wherein said halogen ion is selected from the group consisting of: F−, Cl−, Br−, I−, and mixtures thereof. 9. The method of claim 1, wherein said halogen ion comprises fluorine. 10. The method of claim 1, wherein said solution comprises hydrofluoric acid. 11. The method of claim 1, wherein said solution comprises water, sulfuric acid, and said halogen ions comprise fluoride ions that are present at a concentration of between about 1×10−3 and about 1×10−5. 12. A method of treating an electrically conductive element for use in an electrochemical cell comprising stainless steel having metal oxides on a surface, the method comprising: contacting the surface with an acidic solution having fluoride ions present at a concentration of less than about 1×10−3 to about 1×10−6 molarity for reaction with at least a portion of the metal oxides in the absence of an impressed electrical current, wherein said reaction forms a metal fluoride species soluble in said solution; separating said metal fluoride and said acidic solution from the surface to remove said portion of the metal oxides and to reduce electrical resistance of the surface thereby improving electrical conductivity of the element. 13. The method of claim 12, wherein said contacting is conducted at a temperature of from about 25° C. to about 100° C. 14. The method of claim 12, wherein said contacting is conducted for a duration less than 600 seconds. 15. The method of claim 12, wherein said separating comprises rinsing the surface with a rinse solution, thereby removing said acid solution and said metal fluoride from the surface. 16. The method of claim 12, wherein the metal oxides provide the source of said metal in said metal fluoride and said fluoride ion provides the source of said fluoride in said metal fluoride, whereby the amount of the metal oxides at the surface is lessened. 17. A method of activating a substrate surface of an electrochemical cell, the method comprising: providing a stainless steel alloy substrate comprising one or more elements of iron, chromium, nickel, and molybdenum, wherein said one or more elements form a metal oxide species; determining an instable region of said metal oxide species by thermodynamic phase data; creating a solution for removing of said metal oxide species within said instable region, wherein said solution is at a pH and comprises one or more halogen ions at a concentration of from about 1×10−3 to about to about 1×10−6 molarity such that said solution reacts with said metal oxide species within said instable region; contacting said solution with the substrate surface to react said solution with said metal oxide species to form a metal halide species soluble in said solution; and separating said metal halide soluble species from the substrate surface, thereby removing said metal oxide species and activating the substrate surface. 18. The method of claim 17, wherein said determining includes evaluating thermodynamic phase data at conditions including one or more of pH, temperature, potential energy, and presence of one or more halide anions. 19. The method of claim 17, wherein said solution comprises water, sulfuric acid, and said halogen ions comprise fluoride ions that are present at a concentration of between about 1×10−3 and about 1×10−5, said solution has a pH of from about 2 to about 4, and said contacting is performed at a temperature of from about 25° C. to about 100° C.