# US 11,078,585 B2 · Method for treatment of a chromium finish surface

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- Number: US 11,078,585 B2
- Document ID: US11078585B2
- Status: Granted
- Kind: B2
- Application number: 16/323,603
- Filed: 2017-09-26
- Published: 2019-07-04
- Granted: 2021-08-03
- Earliest claimed: 2016-09-27
- Assignees: Atotech Deutschland GmbH
- Applicants: Atotech Deutschland GmbH
- Inventors: Christina Pfirrmann; Berkem Özkaya; Philipp Wachter; Nancy Born
- Web page: https://patentgrep.com/patent/US11078585B2

## CPC

- C23C 22/18: containing manganese cations
- C25D 3/06: from solutions of trivalent chromium
- C23C 22/06: using aqueous acidic solutions with pH less than 6
- C23C 22/68: using aqueous solutions with pH between 6 and 8
- C25D 5/48: After-treatment of electroplated surfaces
- C25D 9/08: by cathodic processes
- C25D 11/38: Chromatising
- C25D 5/14: two or more layers being of nickel or chromium, e.g. duplex or triplex layers
- C25D 9/06: by anodic processes
- 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

A method for post-treatment of a chromium finish surface to improve corrosion resistance comprising a) providing a substrate having a chromium finish surface, and at least one intermediate layer between the chromium finish surface and the substrate, selected from the group consisting of nickel, nickel alloys, copper and copper alloys, wherein the chromium finish surface is a surface of a trivalent chromium plated layer, obtained by electroplating the substrate, having the at least one intermediate layer, in a plating bath, the plating bath comprising chromium (III) ions; b) contacting the chromium finish surface with an aqueous solution, comprising a permanganate, at least one compound which is selected from a phosphorus-oxygen compound, a hydroxide, a nitrate, a borate, boric acid, a silicate, or a mixture of two or more of these compounds; c) forming a transparent corrosion protection layer onto the chromium finish surface during step b.

## Claims

### Claim 1

A method for post-treatment of a chromium finish surface to improve corrosion resistance, comprising
a) providing a substrate having a chromium finish surface, and at least one intermediate layer between the chromium finish surface and the substrate, wherein the at least one intermediate layer is selected from the group consisting of nickel, nickel alloys, copper and copper alloys, wherein the chromium finish surface is a surface of a trivalent chromium plated layer, obtained by electroplating the substrate having the at least one intermediate layer, in a plating bath, the plating bath comprising chromium (III) ions as a main chromium source;
b) contacting the chromium finish surface with an aqueous solution, comprising
a permanganate, and
at least one compound which is selected from a phosphorus-oxygen compound, a hydroxide, a nitrate, a borate, boric acid, a silicate, or a mixture of two or more of these compounds; and
c) forming a transparent corrosion protection layer onto the chromium finish surface during contacting the chromium surface with the aqueous solution in step b, wherein in step b) an electric potential is applied between the chromium finish surface and an inert counter electrode, wherein the chromium finish surface serves as a cathode and the inert counter electrode serves as an anode.

### Claim 2 (depends on 1)

The method of claim 1, wherein the at least one compound is selected from inorganic phosphorus-oxygen compound as a phosphate, a hydrogenphosphate, a dihydrogenphospate, a pyrophosphate, a phosphonate or mixtures thereof; hydroxide; a borate or a nitrate.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the plating bath is substantially free of chromium (VI) ions and the trivalent chromium plated layer comprises chromium in an amount of 45-90 at % (atom percent), oxygen in an amount of 5-20 at % with the proviso that the total amount of all chemical elements together will not exceed 100 at % and the chromium amount has in every case the highest amount within the trivalent chromium plated layer.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the plating bath is substantially free of chromium (VI) ions and the trivalent chromium plated layer comprises chromium in an amount of 45-90 at %, oxygen in an amount of 5-20 at %, iron in an amount of 0-30 at %, carbon in an amount of 0-15 at %, sulfur in an amount of 0-15 at %, and further metals or nonmetals in an amount of 0-1 at %; with the proviso that the total amount of all chemical elements together will not exceed 100 at % and the chromium amount has in every case the highest amount within the trivalent chromium plated layer.

### Claim 5 (depends on 1)

The method according to claim 1, wherein
one of the at least one intermediate layer, which is directly in contact with the trivalent chromium plated layer, the trivalent chromium plated layer having pores or pores and cracks,
is a bright or satin nickel layer, obtained by electroplating the substrate, and further comprises at least one further intermediate layer which is not a bright nickel layer; or
is a MPS nickel layer, obtained by electroplating the substrate, and further comprises at least one further intermediate layer which is not a MPS nickel layer.

### Claim 6 (depends on 1)

The method of claim 1, wherein a current density of 0.005-5 A/dm2, related to the area of the chromium surface, is generated.

### Claim 7 (depends on 1)

The method of claim 1, wherein the electric potential is applied for 5-900 seconds.

### Claim 8 (depends on 1)

The method according to claim 1, comprising, as a further step
d) treating the chromium surface, after treatment with the aqueous solution in step b), with a component able to reduce and/or dissolve MnO2.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the component is hydrogen peroxide, hydrazine, potassium iodide, sodium sulfite, hydroxylammonium sulfate or a carbohydrate.

### Claim 10 (depends on 8)

The method according to claim 8, wherein the component is selected from sulfuric acid, nitric acid, ascorbic acid and acetic acid.

### Claim 11 (depends on 8)

The method according to claim 8, comprising, as a further step: rinsing the chromium surface after treatment with the aqueous solution in step b), and before treatment with the acid and/or reducing agent in step d).

### Claim 12 (depends on 1)

The method according to claim 1, wherein concentration of permanganate in the aqueous solution is 0.05-4.5 mol/L.

### Claim 13 (depends on 1)

The method according to claim 1, wherein concentration of the phosphorus-oxygen compound, hydroxide, nitrate, borate, boric acid, or silicate in the aqueous solution is 0.05-2 mol/L.

### Claim 14 (depends on 1)

The method according to claim 1, further comprising using the chromium finish surface as a decorative chromium finish surface on a substrate in the automotive, white goods and sanitary industry.

### Claim 15 (depends on 1)

The method according to claim 1, further comprising applying a NSS test (ISO 922 7), wherein the treated chromium finish surface having the transparent corrosion protection layer does not show any alteration of the surface (area of defects: 0%) after applying the NSS test (ISO 922 7) for at least 120 h.