# US 9,435,039 B2 · Protective conversion coating on mixed-metal substrates and methods thereof

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- Number: US 9,435,039 B2
- Document ID: US9435039B2
- Status: Granted
- Kind: B2
- Application number: 13/450,667
- Filed: 2012-04-19
- Published: 2012-08-16
- Granted: 2016-09-06
- Earliest claimed: 2009-08-05
- Assignees: The Curators of the University of Missouri
- Applicants: Matthew J. O'Keefe; Surender Maddela
- Inventors: Matthew J. O'Keefe; Surender Maddela
- Web page: https://patentgrep.com/patent/US9435039B2

## CPC

- C23G 3/00: Apparatus for cleaning or pickling metallic material (with organic solvents C23G5/04)
- C23C 22/68: using aqueous solutions with pH between 6 and 8
- C23G 1/00: Cleaning or pickling metallic material with solutions or molten salts (with organic solvents C23G5/02)
- C25D 13/20: Pretreatment
- C25D 13/22: Servicing or operating {apparatus or multistep processes}
- C23G: CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR

## Abstract

Mixed-metal automotive vehicle bodies-in-white comprising ferrous metal surfaces, zinc surfaces, aluminum alloy surfaces, and magnesium alloy surfaces are cleaned and immersed in an aqueous bath comprising an adhesion promoter and an aqueous electrocoat bath (the adhesion promoter may be in the electrocoat bath. The adhesion promoter, which may be a cerium salt, is selected to react with each metal in the body surfaces to form an oxide layer that provides corrosion resistance for the surface and adherence for the deposited polymeric paint coating. The body is cathodic in the electrocoat deposition.

## Claims

### Claim 1

A method of forming a protective conversion coating on a mixed-metal substrate, the method comprising:
contacting a cerium salt and an oxidizing agent, sufficient to form a protective conversion coating solution;
providing a mixed-metal substrate having a plurality of joined metal surfaces, at least one of the surfaces comprising magnesium, and at least one of the surfaces comprising ferrous metal, zinc, or aluminum; and
depositing the protective conversion coating solution on each metal surface of the mixed-metal substrate to form a protective metal coating conversion solution layer, and wherein any metal present is selected from the group consisting of cerium and one or more metals of the mixed-metal substrate.

### Claim 2 (depends on 1)

The method of claim 1, wherein the oxidizing agent comprises a peroxide compound.

### Claim 3 (depends on 1)

The method of claim 1, wherein the oxidizing agent comprises hydrogen peroxide.

### Claim 4 (depends on 1)

The method of claim 1, wherein depositing comprises spraying.

### Claim 5 (depends on 1)

The method of claim 1, further comprising rinsing the substrate after forming the protective coating.

### Claim 6 (depends on 1)

The method of claim 1, further comprising contacting the protective metal coating conversion solution layer with a phosphate-containing solution.

### Claim 7

A method of forming a protective conversion coating on a mixed-metal substrate, the method comprising:
providing a mixed-metal substrate having a plurality of joined metal surfaces, at least one surface comprising magnesium, and at least one of the surfaces comprising ferrous metal, zinc, or aluminum;
immersing the mixed-metal substrate in an aqueous bath including a dissolved oxidizing composition comprising metal cations capable of forming a conversion coating with each metal surface of the mixed-metal substrate; wherein the metal cations are selected from a group consisting of cerium cations, the conversion coating includes cerium and oxygen, and the metal cations react with each of the metal surfaces of the mixed-metal substrate upon immersion to form a conversion coating on each metal surface of the mixed-metal substrate.

### Claim 8 (depends on 7)

The method of claim 7, wherein the dissolved oxidizing composition comprises at least one of the compounds selected from the group consisting of cerium-based compounds, silicon-based compounds, titanium-based compounds, vanadium-based compounds, and zirconium-based compounds.

### Claim 9 (depends on 7)

The method of claim 7, wherein the oxidizing composition comprises a cerium-based compound.

### Claim 10 (depends on 7)

The method of claim 7, wherein the oxidizing composition comprises cerium trichloride.

### Claim 11 (depends on 7)

The method of claim 7, wherein the thicknesses of the conversion coating is up to about 500 nanometers.

### Claim 12 (depends on 7)

The method of claim 7, further comprising sequentially cleaning the surfaces of the substrate with one of an alkaline cleaner and an acid cleaner, and then with the other cleaner, before the substrate is immersed in a bath comprising a dissolved oxidizing solution.

### Claim 13 (depends on 7)

The method of claim 7, further comprising contacting the conversion coating with a phosphate-containing solution.

### Claim 14

A method of forming a protective conversion coating on a mixed-metal substrate, the method comprising:
providing a mixed-metal substrate having a plurality of joined metal surfaces including a first surface comprising magnesium, and a second metal surface different from the first surface; and
immersing the mixed-metal substrate in an aqueous bath including a dissolved oxidizing composition comprising cerium cations capable of forming a conversion coating with each metal surface of the mixed-metal substrate, wherein the conversion coating includes cerium and oxygen, and the cerium cations react with each of the metal surfaces of the mixed-metal substrate upon immersion to form a conversion coating on the surface of each metal of the mixed-metal substrate.

### Claim 15 (depends on 14)

The method of claim 14, further comprising contacting the conversion coating with a phosphate-containing solution.

### Claim 16

A method of forming a protective conversion coating on a mixed-metal substrate, the method comprising:
contacting a cerium salt and an oxidizing agent, sufficient to form a protective conversion coating solution;
providing a mixed-metal substrate having a plurality of joined metal surfaces including a first surface comprising magnesium, and a second metal surface different from the first surface; and
depositing the protective conversion coating solution on each metal surface of the mixed-metal substrate to form a protective coating conversion solution layer; wherein the conversion coating solution comprises an accelerator selected from the group consisting of a peroxide compounds.

### Claim 17 (depends on 16)

The method of claim 16, wherein the peroxide compound comprises hydrogen peroxide.

### Claim 18 (depends on 16)

The method of claim 16, further comprising contacting the protective coating conversion solution layer with a phosphate-containing solution.