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Composition and method for surface treatment of oxidized metal

a technology of oxidized metal and composition, applied in the preparation of detergent mixture compositions, electrochemical generators, inorganic non-surface active detergent compositions, etc., can solve the problems of reducing the performance increasing the internal resistance of the fuel cell,

Inactive Publication Date: 2005-02-17
GENERAL MOTORS COMPANY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005] The present invention relates to metallic substrate such as an electrically conductive element which in one preferred embodiment comprises an electrically conductive corrosion susceptible metal substrate having a co...

Problems solved by technology

Unfortunately, many metals are susceptible to corrosion in the hostile PEM fuel cell environment, and contact elements made therefrom either dissolve (e.g., in the case of aluminum), or form highly electrically resistive, passivating oxide films on their surface (e.g., in the case of titanium or stainless steel) that increases the internal resistance of the fuel cell and reduces its performance.

Method used

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  • Composition and method for surface treatment of oxidized metal
  • Composition and method for surface treatment of oxidized metal
  • Composition and method for surface treatment of oxidized metal

Examples

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example 1

[0063] An electrically conductive element according to a preferred embodiment of the present invention is prepared by providing stainless steel strips samples measuring approximately 31 cm×18 cm×0.02 cm. The stainless steel is Type 316L, cold rolled, bright annealed, strip, UNS S31603 in accordance with ASTM A480 from Arcelor, S.A. located in Grand-Duché, Luxembourg. The steel substrate is pre-cleaned by spraying an alkaline cleaning solution of PARCO® Clean 1200 (an alkaline cleaner with a builder constituent comprising potassium hydroxide and tetrapotassium pyrophosphate) at 5 wt % and 95 wt % deionized water for 10 seconds at 71° C. A deionized water rinse is sprayed onto the surface to remove any residual alkaline cleaning solution.

[0064] An acidic treatment solution is prepared by admixing 3 wt % sulfuric acid solution; 97 wt % deionized water solvent; and 284 ppm of HF. The sulfuric acid can be purchased as Ridolene® 123, available from Henkel Surface Technologies of Madison ...

example 2

[0066] An electrically conductive element prepared according to an alternate preferred embodiment of the present invention is prepared by providing the same stainless steel strips samples as those in Example 1. The steel substrate is pre-cleaned with the same alkaline cleaning solution and rinse solution as in Example 1.

[0067] An acidic treatment solution is prepared by admixing 3 wt % sulfuric acid solution; 97 wt % deionized water solvent; and 568 ppm of HF. The sulfuric acid is provided as Ridolene® 123, as used in Example 1. The hydrofluoric acid can be purchased from VWR Scientific Products Inc. The acidic treatment solution is sprayed on the steel substrate surface for 10 seconds at 66° C. to activate the surface and remove metal oxides. The steel substrate is then rinsed, dried, and coated in the same manner as the conductive element described in Example 1.

example 3

[0068] An electrically conductive element prepared according to another alternate preferred embodiment of the present invention is prepared by providing the same stainless steel strips samples as those described in Example 1. The steel substrate is pre-cleaned at the same conditions with the same alkaline cleaning solution and rinse solution as in Example 1.

[0069] An acidic treatment solution is prepared by admixing 3 wt % sulfuric acid solution and 97 wt % deionized water solvent. The sulfuric acid is provided as Ridolene® 123, as used in Example 1. The acidic treatment solution is sprayed on the steel substrate surface for 10 seconds at 66° C. to activate the surface and remove metal oxides. The steel substrate is then rinsed, dried, and coated in the same manner as the conductive element described in Example 1.

[0070] Immediately after the application of acidic treatment solution and before the protective coating in Examples 1, 2, and 3, the contact resistance measurements of th...

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Abstract

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.

Description

FIELD OF THE INVENTION [0001] The present invention relates to composition and method for surface treatment of oxidized metal and more particularly to such as applied to preparation of corrosion-resistant electrically conductive elements. BACKGROUND OF THE INVENTION [0002] Fuel cells have been proposed as a power source for electric vehicles and other applications. One known fuel cell is the PEM (i.e., Proton Exchange Membrane) fuel cell that includes a so-called MEA (“membrane-electrode-assembly”) comprising a thin, solid polymer membrane-electrolyte having an anode on one face and a cathode on the opposite face. The anode and cathode typically comprise finely divided carbon particles, very finely divided catalytic particles supported on the internal and external surfaces of the carbon particles, and proton conductive material intermingled with the catalytic and carbon particles. The MEA is sandwiched between a pair of electrically conductive contact elements which serve as current...

Claims

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Application Information

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IPC IPC(8): C11D1/00C11D7/10C11D11/00C23FC23G1/02
CPCC11D11/0029C11D7/10C23G1/081C23G1/086H01M8/021H01M8/0258H01M8/0254H01M2008/1095Y02E60/50C11D2111/16
Inventor ABD ELHAMID, MAHMOUD H.MIKHAIL, YOUSSEF
Owner GENERAL MOTORS COMPANY
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