# US 4,391,652 A · Surface treatment for aluminum and aluminum alloys

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- Number: US 4,391,652 A
- Document ID: US4391652A
- Status: Granted
- Kind: A
- Application number: 06/343,992
- Filed: 1982-01-29
- Granted: 1983-07-05
- Earliest claimed: 1982-01-29
- Assignees: Chemical Systems, Inc.
- Inventors: Narayan Das; Joy M. Schaefer
- Web page: https://patentgrep.com/patent/US4391652A

## CPC

- C23C 22/361: {containing titanium, zirconium or hafnium compounds}
- C23C 22/34: containing fluorides or complex fluorides
- 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)

## Abstract

A low pH solution and a method for conversion coating aluminum and aluminum alloy surfaces, as well as the coated surfaces themselves, utilizing zirconium, fluoride and nickel and, optionally, fluorophosphate.

## Claims

### Claim 1

An aqueous coating solution for forming a coating on aluminum and aluminum alloy surfaces consisting essentially of at least about 0.025 grams/liter of zirconium, at least about 0.050 grams/liter of fluoride ion, at least about 0.025 grams/liter of nickel and sufficient acid to adjust the pH to the range of about 1.2 to about 2.5.

### Claim 2 (depends on 1)

An aqueous coating solution as in claim 1 including at least 10 ppm by weight of phosphate.

### Claim 3 (depends on 1)

An aqueous coating solution as in claim 1 including at least about 0.050 grams/liter of fluorophosphate.

### Claim 4 (depends on 1, 2, 3)

An aqueous coating solution as in claim 1, 2 or 3 including at least about 0.050 grams/liter of a polyhydroxy compound having up to 7 carbon atoms.

### Claim 5 (depends on 4)

An aqueous coating solution as in claim 4 wherein said polyhydroxy compound is sodium glucoheptonate.

### Claim 6 (depends on 1, 2, 3)

An aqueous coating solution as in claims 1, 2 or 3 wherein said zirconium is present at a level of at least about 0.08 grams/liter, said fluoride is present at a level of at least about 0.100 grams/liter and said nickel is present at a level of at least about 0.100 grams/liter.

### Claim 7 (depends on 1, 2, 3)

An aqueous coating solution as in claim 1, 2 or 3 wherein said pH is adjusted to the range of about 1.5 to about 2.0.

### Claim 8

An aqueous coating solution for forming a protective, flexible coating on aluminum and aluminum alloy surfaces consisting essentially of from about 0.05 to about 0.120 grams/liter of zirconium, from about 0.100 to about 0.150 grams/liter of fluoride, from about 0.075 to about 0.150 grams/liter of nickel, from about 0.100 to about 0.150 grams/liter of a fluorophosphate compound, from 0.075 to about 0.150 grams/liter of a polyhydroxy compound having up to 7 carbon atoms and sufficient acid to adjust the pH of the solution to the range of about 1.5 to about 2.0.

### Claim 9

A method for coating aluminum and aluminum alloy surfaces comprising contacting said surfaces with an aqueous coating solution consisting essentially of at least about 0.025 of zirconium, at least about 0.050 of fluoride, at least 0.025 of nickel and sufficient acid to adjust the pH of said solution to the range of about 1.2 to about 2.5.

### Claim 10 (depends on 9)

A coating method as in claim 9, wherein said pH is adjusted to the range of about 1.5 to about 2.0.

### Claim 11 (depends on 9)

A coating method as in claim 9 wherein the temperature of said coating solution is adjusted to the range of about 80.degree. F. to about 150.degree. F.

### Claim 12 (depends on 9)

A coating method as in claim 9 wherein the temperature of said coating solution is adjusted to the range of about 110.degree. F. to about 130.degree. F.

### Claim 13 (depends on 9)

A coating method as in claim 9 wherein said surfaces are cleaned with an alkaline cleaner before said surfaces are contacted with said coating solution.

### Claim 14 (depends on 9, 10, 11, 12, 13)

A coating method as in claim 9, 10, 11, 12 or 13 wherein said surface is contacted with said coating solution for from about 3 to about 10 seconds.

### Claim 15 (depends on 9, 10, 11, 12, 13)

A coating method as in claim 9, 10, 11, 12 or 13 wherein said surface is contacted with said coating solution for from about 10 to about 30 seconds.