# US 2018/0022938 A1 · Corrosion inhibitor-incorporated layered double hydroxide and sol-gel coating compositions and related processes

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- Number: US 2018/0022938 A1
- Document ID: US20180022938A1
- Status: Published application
- Kind: A1
- Application number: 15/231,668
- Filed: 2016-08-08
- Published: 2018-01-25
- Earliest claimed: 2016-07-20
- Assignees: The Boeing Company
- Applicants: The Boeing Company
- Inventors: Vijaykumar S. Ijeri; Om Prakash; Stephen P. Gaydos; Raghavan Subasri; Kalidindi Ramachandra Soma Raju; Dendi Sreenivas Reddy
- Web page: https://patentgrep.com/patent/US20180022938A1

## CPC

- C09D 5/106: {containing Zn}
- B05D 3/06: by exposure to radiation (B05D3/02 takes precedence {; plasma treatment B05D3/141})
- C23C 18/1208: {Oxides, e.g. ceramics}
- C23C 18/1237: {Composite substrates, e.g. laminated, premixed}
- C23C 18/1254: {Sol or sol-gel processing}
- C23C 18/1295: {with after-treatment of the deposited inorganic material}
- C23C 22/66: Treatment of aluminium or alloys based thereon
- C23C 22/68: using aqueous solutions with pH between 6 and 8
- C23C 22/83: Chemical after-treatment
- C23F 11/06: in markedly alkaline liquids
- C23F 11/173: Macromolecular compounds
- C23C 2222/20: Use of solutions containing silanes
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- B05D: PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL (conveying articles or workpieces through baths of liquid B65G, e.g. B65G49/02)
- 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)
- C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25

## Abstract

A corrosion-resistant coating on an aluminum-containing substrate such as an aluminum substrate, an aluminum alloy substrate (e.g., AA 2024, AA 6061, or AA7075), or other aluminum-containing substrate includes a corrosion inhibitor-incorporated Zn—Al layered double hydroxide (LDH) layer and a sol-gel layer. A zinc salt and a corrosion inhibitor (e.g., a salt of an oxyanion of a transition metal such as a vanadate) is dissolved to form a zinc-corrosion inhibitor solution, and the substrate is immersed in or otherwise contacted with the solution to form the corrosion inhibitor-incorporated Zn—Al LDH layer on the substrate. A sol-gel composition is applied on the corrosion inhibitor-incorporated Zn—Al LDH layer of the substrate to form a sol-gel layer, and the sol-gel layer is cured.

## Claims

### Claim 1

A method for providing a corrosion-resistant coating on a substrate, the method comprising:
preparing a zinc-corrosion inhibitor solution by dissolving a zinc salt and a corrosion inhibitor, the corrosion inhibitor comprising a salt of an oxyanion of a transition metal; and
contacting the substrate comprising an aluminum alloy with the zinc-corrosion inhibitor solution to form a corrosion inhibitor-incorporated Zn—Al layered double hydroxide (LDH) layer on the substrate, wherein the aluminum alloy comprises 2024 aluminum alloy, 6061 aluminum alloy, or 7075 aluminum alloy.

### Claim 2 (depends on 1)

The method of claim 1, wherein the preparing the zinc-vanadate solution comprises:
dissolving the zinc salt in a first aqueous media to form a first solution;
adjusting the first solution to a pH ranging from about 6 to about 8;
dissolving the corrosion inhibitor in a second aqueous media to form a second solution, the corrosion inhibitor comprising a vanadate, a manganate, a permanganate, a molybdate, a tungstate, or a combination thereof;
adjusting the second solution to a pH ranging from about 8 to about 10; and
mixing the first and second solution to form the zinc-corrosion inhibitor solution.

### Claim 3 (depends on 2)

The method of claim 2, wherein the dissolving the zinc salt comprises dissolving zinc nitrate in an amount ranging from about 5 to about 30 parts by weight per 100 parts by weight of the first solution.

### Claim 4 (depends on 2)

The method of claim 2, wherein the dissolving the corrosion inhibitor comprises dissolving sodium metavanadate in an amount ranging from of about 0.1 to about 2 parts by weight per 100 parts by weight of the second solution, and wherein the zinc-corrosion inhibitor solution has a ratio of a number of moles of zinc to a number of moles of vanadium (nZn/nV) ranging from about 5 to about 100.

### Claim 5 (depends on 2)

The zinc-corrosion inhibitor solution prepared according to the method of claim 2.

### Claim 6 (depends on 1)

The method of claim 1, wherein the contacting comprises maintaining a pH ranging from about 8 to about 10 and a temperature ranging from about 70 to about 90° C. for a time period ranging from about 1 to about 6 h.

### Claim 7 (depends on 1)

The corrosion-resistant coating comprising the corrosion inhibitor-incorporated Zn—Al LDH layer formed by the method of claim 1.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
contacting a sol-gel composition on the corrosion inhibitor-incorporated Zn—Al LDH layer of the substrate to form a sol-gel layer; and
curing the sol-gel layer.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
contacting an alkoxysilane with water and an inorganic acid to form a first composition;
contacting a zirconium alkoxide with a first organic acid to form a second composition; and
mixing the first composition with the second composition to form the sol-gel composition.

### Claim 10 (depends on 9)

The method of claim 9, wherein the contacting to form the first composition comprises mixing the alkoxysilane having the formula RA—Si—(RB)3 with the water and the inorganic acid, wherein the RA is methacryloxyalkyl or glycidyloxyalkyl, and wherein the RB is a methoxy or ethoxy.

### Claim 11 (depends on 9)

The method of claim 9, wherein the contacting to form the second composition comprises mixing the zirconium alkoxide having the formula Zr—(RC)4 with methacrylic acid (MAA), and wherein the RC is ethoxy, n-propoxy, isopropoxy, n-butyloxy, or tert-butyloxy.

### Claim 12 (depends on 9)

The method of claim 9, further comprising:
adding an additional alkoxysilane and MAA to the sol-gel composition, the additional alkoxysilane having the formula RD—Si—(RE)3, wherein the RD is aryl, aminoalkyl, or glycidoxyalkyl, and wherein the RE is methoxy or ethoxy.

### Claim 13 (depends on 9)

The method of claim 9, further comprising:
adding a corrosion inhibiting compound to the sol-gel composition in an amount ranging from about 1 to about 5 parts by weight per 100 part by weight of the sol-gel composition.

### Claim 14 (depends on 13)

The method of claim 13, wherein the adding the corrosion inhibiting compound comprises adding a vanadate, a molybdate, a phosphate, a manganate, a permanganate, a titanate, titania, an aluminate, alumina, ceria, a ceric salt, a cerous salt, or combination thereof.

### Claim 15 (depends on 8)

The method of claim 8, wherein the curing the sol-gel layer comprises exposing the sol-gel layer to a temperature ranging from about 70 to about 90° C. for a time period ranging from about 30 to about 120 min in a hot air circulated oven.

### Claim 16 (depends on 8)

The method of claim 8, wherein the curing the sol-gel layer comprises exposing the sol-gel layer to infrared (IR) radiation and/or near IR radiation.

### Claim 17 (depends on 8)

The method of claim 8, further comprising applying primer or paint on the sol-gel layer of the substrate, the sol-gel layer facilitating adherence of the primer or the paint to the substrate.

### Claim 18 (depends on 8)

The corrosion-resistant coating comprising the corrosion inhibitor-incorporated Zn—Al LDH layer and the sol-gel layer formed by the method of claim 8.

### Claim 19

A corrosion-resistant coated product, comprising:
a corrosion inhibitor-incorporated Zn—Al layered double hydroxide (LDH) layer on an aluminum alloy substrate, the corrosion inhibitor comprising a salt of an oxyanion of a transition metal, wherein the aluminum alloy substrate comprises 2024 aluminum alloy, 6061 aluminum alloy, or 7075 aluminum alloy; and
a sol-gel layer on the corrosion inhibitor-incorporated Zn—Al LDH layer of the substrate, the sol-gel layer comprising a polymer composite of one or more alkoxysilanes and a zirconium alkoxide.

### Claim 20 (depends on 19)

The corrosion-resistant coated product of claim 19, wherein the sol-gel layer contains a corrosion inhibiting compound comprising a vanadate, a molybdate, a phosphate, a manganate, a permanganate, a titanate, titania, an aluminate, alumina, ceria, a ceric salt, a cerous salt, or combination thereof.