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Publication numberUS3637354 A
Publication typeGrant
Publication dateJan 25, 1972
Filing dateSep 24, 1969
Priority dateSep 24, 1969
Publication numberUS 3637354 A, US 3637354A, US-A-3637354, US3637354 A, US3637354A
InventorsDonald R Zaremski
Original AssigneeAllegheny Ludlum Steel
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Trim members
US 3637354 A
Abstract
The application describes assemblies comprised of a body member in combination with a stainless steel trim member having a contact surface which abuts the body member and an exposure surface subject to view. Adhered to the contact surface and located between the contact surface and the body member is a layer of aluminum which provides galvanic protection for the body member. Covering the aluminum is a chromate or phosphate conversion coating which provides protection against aluminum galvanic corrosion without detrimentally affecting the galvanic protection which aluminum provides for the body member. Also described are conversion-coated, aluminum-striped stainless steel composites suitable for fabrication into trim members and a method for producing conversion-coated, aluminum-striped stainless steel trim members.
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Description  (OCR text may contain errors)

United States Patent 1151 3,6 Zaremski [451 Jan. 25, 1972 [54] TRIM MEMBERS Attorney-Richard A. Speer, Vincent G. Gioia and Howard R.

B k t k, [72] Inventor: Donald R. Zaremski, Cheswick, Pa. er ens 0c Jr [73] Assignee: Allegheny Ludlum Steel Corporation, Pitt- [57] ABSTRACT sburgh' The application describes assemblies comprised of a body [22] Filed; Sept 24 19 9 member in combination with a stainless steel trim member Appl. No.: 860,541

Primary Examiner-L. Dewayne Rutledge Assistant ExaminerE. L. Weise having a contact surface which abuts the body member and an exposure surface subject to view. Adhered to the contact surface and located between the contact surface and the body member is a layer of aluminum which provides galvanic protection for the body member. Covering the aluminum is a chromate or phosphate conversion coating which provides protection against aluminum galvanic corrosion without detrimentally affecting the galvanic protection which aluminum provides for the body member. Also described are conversioncoated, aluminum-striped stainless steel composites suitable for fabrication into trim members and a method for producing conversion-coated, aluminum-striped stainless steel trim members.

12 Claims, 2 Drawing Figures PATENTED JAN25 I972 INVEN TOR. DONALD R. ZAREMSK/ Attorney TRIM MEMBERS The present invention relates to stainless steel composites in the form of trim members and more particularly to conversion-coated, aluminum-striped stainless steel composites in the form of trim members. It further relates to conversioncoated, aluminum-striped stainless steel composites suitable for fabrication into trim members and to assemblies comprised of conversion-coated, aluminum-striped stainless steel trim members in combination with body members.

Stainless steel is known to serve a particularly good purpose in those applications where brightness and stain resistance to a variety of contaminants is required and is ideally suited for use as automotive trim. However, since most automotive bodies are constructed of carbon steel, the use of stainless steel can result in galvanic corrosion. Carbon steel is anodic to stainless steel and generally corrodes in the vicinity of stainless steel in the presence of an electrolyte, such as moisture.

To protect carbon steel it has been the practice to coat stainless strips with a nonferrous sacrificial metal which is anodic to mild carbon steel prior to or after forming the strips into trim members. The coating is preferably aluminum. It is applied to those sections of the strip which will eventually contact the automotive body, i.e., the return flange of the fabricated trim member.

Testing under normal road conditions has indicated that the use of aluminum solves the galvanic corrosion problem faced by automotive manufacturers. However, when the aluminum corrodes, it results in the formation and bleeding of aesthetically objectionable aluminum corrosion products (white corrosion products).

I have discovered that the formation and bleeding of aluminum corrosion products can be minimized without adversely affecting the galvanic protection provided by the aluminum, through application of a protective chromate or phosphate conversion coating to the aluminum. These coatings have been applied in nonrelated environments to aluminum for protection against general corrosion and to very thin layers of zinc, for protection against galvanic corrosion. My work has shown that they offer protection against aluminum galvanic corrosion without detrimentally affecting the galvanic protection which aluminum provides for carbon steel in the vicinity of stainless steel.

It is accordingly an object of this invention to provide a conversion-coated, aluminum-striped stainless steel composite.

It is a further object of this invention to provide an assembly comprised of a body member in combination with a conversion-coated, aluminum-striped stainless steel trim member which provides galvanic protection for the body member.

The foregoing and other objects of the invention will be best understood from the following description, reference being had to the accompanying drawing, wherein:

FIG. 1 is a sectional view of a stainless steel trim member; and

FIG. 2 is a perspective view of a stainless steel trim member.

The present invention encompasses a composite suitable for fabrication into a stainless steel trim member, a composite in the form of a stainless steel trim member, a method for producing stainless steel trim members and an assembly comprising a stainless steel trim member in combination with a body member. The body member is comprised of metal, e.g., plain carbon steel, which is less noble in the electromotive series than stainless steel. In the context of this application, the term metal is interpreted as including metal which is painted and coated as well as bare.

The stainless steel trim member has a contact surface and an exposure surface. The contact surface abuts the body member after assembly and the exposure surface is subject to view. Adhered to the contact surface is a layer of aluminum. The aluminum is generally at least 0.5 of a mil thick and preferably between 3 and 5 mils. Covering the aluminum is a conversion coating from the group consisting of chromate and phosphate conversion coatings.

FIGS. 1 and 2 are respectively a sectional and perspective view of a stainless steel trim member 1 which meets the requirements of this invention. It comprises an exposed surface 2, contact surfaces 4, aluminum stripes 6, and conversion coatings 8.

The method of this invention includes the steps of shaping a stainless steel sheet into a trim member having an exposed surface and at least one contact surface and adhering aluminum to those portions of the sheet which are the contact surfaces of the finally formed trim member. Any of the well-known methods of shaping, e.g., roll forming, and adhering; e.g., roll pressure bonding, are within the scope of this invention. The method additionally involves the step of applying a conversion coating to the aluminum either before or after shaping. It can be any of the well-known chromate or phosphate conversion coatings. A typical chromate conversion coating consists of 0.99 ounces of sodium dichromate, 0.132 ounces of sodium fluoride, 0.66 ounces of potassium ferricyanide, 3 cubic centimeters of nitric acid, and 1 gallon of water. It is applied at a temperature between ambient and l30 F. for a period of time between 5 seconds and 8 minutes. A typical phosphate conversion coating consists of 1 gallon of water and 10-20 ounces of solution composed of 61.7 percent ammonium phosphate, 22.9 percent ammonium fluoride, and 15.4 percent potassium dichromate. It is applied at a temperature between 1 l0 and 120 F. for a period of time between I and 5 minutes.

The following example illustrates several aspects of the invention.

A number of stainless steel trim members were prepared withstripes of aluminum adhered to their contact surface. Half of the trim members were assembled onto carbon steel body members without further treatment. The other half were given a chromate conversion coating prior to assembly. Coating was accomplished by dipping the aluminum stripes into a bath maintained at ambient temperature. Immersion times ranged from 1 to 3 minutes. The bath contained Iridite No. l42, a chromate conversion coating sold by Allied Research Products, Inc., Baltimore, Md.

All of the assemblies, i.e., those with and those without chromate conversion coatings, were subject to salt spray tests in order to demonstrate the effectiveness of the conversion coatings. These tests are considered to be accelerated tests insofar as they produce corrosive conditions far more severe than those encountered by automotive bodies under normal road conditions. Aluminum corrosion products were well in evidence on the untreated assemblies, i.e., those without chromate conversion coatings, after 24 hours of testing. The treated assemblies, i.e., those with chromate conversion coatings, were essentially free of aluminum corrosion products after hours of testing and provided the carbon steel body member with galvanic protection equivalent to that provided by the untreated assemblies.

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with specific examples thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific examples of the invention described herein.

Iclaim:

I. An assembly comprising a stainless steel trim member in combination with a first metal less noble in the electromotive series than stainless steel; said stainless steel trim member having an exposed surface and a contact surface abutting said first metal, a layer of aluminum adhering to said contact surface, said aluminum being less noble in the electromotive series than said first metal, and a conversion coating from the group consisting of chromate and phosphate conversion coatings on said aluminum. said coated aluminum acting to preclude galvanic action between said first metal and said stainless steel.

2. An assembly according to claim 1 wherein said first metal is plain carbon steel.

3. An assembly according to claim 1 wherein said conversion coating is a chromate conversion coating.

4. An assembly according to claim I wherein said conversion coating is a phosphate conversion coating.

9. A composite article according to claim 7 wherein said conversion coating is a phosphate conversion coating.

10. A composite article according to claim 7 having at least two spaced-apart stripes of aluminum.

II. A composite article according to claim 7 wherein said aluminum has a thickness in excess of about 0.5 of a mil.

12. A composite article according to claim I] wherein said aluminum has a thickness of from about 3 mils to about 5 mils.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3201210 *Jan 3, 1963Aug 17, 1965Allegheny Ludlum SteelTrim member assembly
US3201211 *Jun 22, 1962Aug 17, 1965Allegheny Ludlum SteelStainless steel trim member
US3201212 *Jun 22, 1962Aug 17, 1965Allegheny Ludlum SteelTrim member
US3484350 *Apr 28, 1965Dec 16, 1969Allegheny Ludlum SteelMethod of producing trim members
US3536459 *Nov 29, 1967Oct 27, 1970United States Steel CorpStainless steel composite
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3859061 *Apr 23, 1973Jan 7, 1975Chromalloy American CorpCorrosion resistant coating system for ferrous metal articles having brazed joints
US3948689 *Oct 9, 1973Apr 6, 1976Alloy Surfaces Company, Inc.Chromic-phosphoric acid coated aluminized steel
US4885215 *Sep 29, 1987Dec 5, 1989Kawasaki Steel Corp.Zn-coated stainless steel welded pipe
Classifications
U.S. Classification428/601, 428/595, 428/926, 428/933, 428/653, 428/628
International ClassificationC23C22/37, C23C22/06, C23F13/02
Cooperative ClassificationC23F13/02, C23C22/06, Y10S428/926, C23C22/37, Y10S428/933
European ClassificationC23F13/02, C23C22/37, C23C22/06
Legal Events
DateCodeEventDescription
Jan 3, 1989ASAssignment
Owner name: PITTSBURGH NATIONAL BANK
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. RECORDED ON REEL 4855 FRAME 0400;ASSIGNOR:PITTSBURGH NATIONAL BANK;REEL/FRAME:005018/0050
Effective date: 19881129
Jan 3, 1989AS02Assignment of assignor's interest
Owner name: PITTSBURGH NATIONAL BANK
Effective date: 19881129
Mar 24, 1987ASAssignment
Owner name: PITTSBURGH NATIONAL BANK
Free format text: SECURITY INTEREST;ASSIGNOR:ALLEGHENY LUDLUM CORPORATION;REEL/FRAME:004855/0400
Effective date: 19861226
Dec 29, 1986ASAssignment
Owner name: ALLEGHENY LUDLUM CORPORATION
Free format text: CHANGE OF NAME;ASSIGNOR:ALLEGHENY LUDLUM STEEL CORPORATION;REEL/FRAME:004779/0642
Effective date: 19860805
Dec 29, 1986AS01Change of name
Owner name: ALLEGHENY LUDLUM CORPORATION
Effective date: 19860805
Owner name: ALLEGHENY LUDLUM STEEL CORPORATION