# US 11,078,573 B2 · Method for producing a steel product with a Zn coating and a tribologically active layer deposited on the coating, and a steel product produced according to said method

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- Number: US 11,078,573 B2
- Document ID: US11078573B2
- Status: Granted
- Kind: B2
- Application number: 16/070,809
- Filed: 2016-01-19
- Published: 2019-01-24
- Granted: 2021-08-03
- Earliest claimed: 2016-01-19
- Assignees: thyssenkrupp AG; ThyssenKrupp Steel Europe AG
- Applicants: ThyssenKrupp Steel Europe AG; thyssenkrupp AG
- Inventors: Thomas Lostak; Christian Timma
- Web page: https://patentgrep.com/patent/US11078573B2

## CPC

- C23C 22/53: Treatment of zinc or alloys based thereon
- C23C 2/26: After-treatment (C23C2/14 takes precedence)
- C23C 22/78: Pretreatment of the material to be coated
- C23C 2/06: Zinc or cadmium or alloys based thereon
- C23C 2/40: Plates; Strips
- 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 process for producing a steel product having a protective coating based on zinc and a tribologically active layer applied to the protective coating where the process includes providing a flat steel product provided with the protective coating, and applying an aqueous solution comprising ammonium sulfate and demineralized water to the protective coating of the steel product. The concentration of the ammonium sulfate based on the SO42− ions is 0.01-5.7 mol/L, the pH of the aqueous solution is 4-6, and the near-surface reaction time between the aqueous solution and the protective coating is more than 0 seconds and not more than 5 seconds. After a drying operation conducted without preceding rinsing, a tribologically active layer consisting of ammonium zinc sulfate is formed atop the protective zinc coating. Also, a steel product having a protective coating based on zinc and a tribologically active layer of ammonium zinc sulfate.

## Claims

### Claim 1

A process for producing a steel product having a protective coating based on zinc and a tribologically active layer applied to the protective coating, comprising the following steps:
providing a steel product provided with the protective coating;
applying an aqueous solution comprising ammonium sulfate and demineralized water to the protective coating of the steel product;
wherein the concentration of the ammonium sulfate based on the SO42− ions is 0.01-5.7 mol/L,
wherein the pH of the aqueous solution is 4-6, and
wherein the near-surface reaction time between the aqueous solution and the protective coating is more than 0 seconds and not more than 5 seconds, such that, after a drying operation conducted without preceding rinsing, there is a tribologically active layer consisting of ammonium zinc sulfate atop the protective coating.

### Claim 2 (depends on 1)

The process as claimed in claim 1, wherein the concentration of the ammonium sulfate in the aqueous solution based on the SO42− ions is 0.1-3 mol/L.

### Claim 3 (depends on 2)

The process as claimed in claim 2, wherein the concentration of the ammonium sulfate in the aqueous solution based on the SO42− ions is 0.4-0.7 mol/L.

### Claim 4 (depends on 1)

The process as claimed in claim 1, wherein the pH of the aqueous solution is 4.2-5.7.

### Claim 5 (depends on 1)

The process as claimed in claim 1, wherein the steel product is a flat steel product.

### Claim 6 (depends on 1)

The process as claimed in claim 1, wherein the aqueous solution is applied to the protective coating by a chemcoater or coil coater.

### Claim 7 (depends on 1)

The process as claimed in claim 1, wherein the steel product, after the aqueous solution has been applied, is dried at a temperature of 70-90° C.

### Claim 8 (depends on 1)

The process as claimed in claim 1, wherein the surface of the steel product to be coated is subjected to alkaline cleaning prior to the coating operation.

### Claim 9

A steel product comprising a steel substrate and a protective coating based on zinc borne by the steel substrate, wherein a tribologically active layer consisting of ammonium zinc sulfate has been formed atop the protective coating.

### Claim 10 (depends on 9)

The steel product as claimed in claim 9, wherein the dry coat weight of the tribologically active layer is 1-100 mg/m2 based on the sulfur content.

### Claim 11 (depends on 10)

The steel product as claimed in claim 10, wherein the dry coat weight of the tribologically active layer is 10-50 mg/m2 based on the sulfur content.

### Claim 12 (depends on 11)

The steel product as claimed in claim 11, wherein the dry coat weight of the tribologically active layer is 10-20 mg/m2 based on the sulfur content.