Surface treatment composition

Patent metadata

Field	Value
Publication number	US-10745568-B2
Application number	US-201615568532-A
Country	US
Kind code	B2
Filing date	Jun 1, 2016
Priority date	Jun 3, 2015
Publication date	Aug 18, 2020
Grant date	Aug 18, 2020

Abstract

The present invention relates to an acidic aqueous composition for treating of zirconium-pretreated metal-based substrate surfaces such as steel metals or aluminium surfaces, a process for treating the substrate surfaces with the composition and the use of the composition as post-treatment of zirconium-pretreated metal-based substrate surfaces for subsequent electrocoating of the surfaces to increase corrosion resistance of said metal-based surfaces prior to electro-coating (e-coat) applications and increases detergent and chemical resistance of treated surfaces used in the white goods industry. The acidic aqueous composition comprises trivalent chromium ions; and hexafluorozirconate ions; characterized in that the source of trivalent chromium ions is a trivalent chromium nitrate salt.

First claim

The invention claimed is:

1. A process for treating of zirconium-pretreated metal-based substrate surfaces, comprising: i providing a zirconium-pretreated metal-based substrate; and ii. applying to surfaces of the substrate an acidic aqueous composition comprising: a. trivalent chromium ions; and b. hexafluorozirconate ions; characterized in that the sole source of the trivalent chromium ions is a trivalent chromium nitrate salt.

2. The process according to claim 1 wherein the concentration of trivalent chromium ions ranges between 10 and 5,000 mg/L.

3. The process according to claim 1 wherein the zirconium-pretreated metal-based substrate surfaces are obtained by pretreating with an aqueous chromium ion-free composition comprising hexafluorozirconate ions.

4. The process according to claim 1 wherein the trivalent chromium nitrate salt is Cr(NO 3 ) 3 or Cr(NO 3 ) 3 ·9 H 2 O.

5. The process according to claim 1 wherein the concentration of hexafluorozirconate ions independently ranges between 10 and 10,000 mg/L.

6. The process according to claim 1 wherein the source of hexafluorozirconate ions independently is selected from the group consisting of hexafluorozirconic acid, ammonium hexafluorozirconate, an alkali metal hexafluorozirconate, an alkaline earth metal hexafluorozirconate and a transition metal hexafluorozirconate.

7. The process according to claim 1 wherein a pH value of the acidic aqueous composition ranges between 2.0 and 5.5.

8. The process according to claim 1 wherein the acidic aqueous composition is free from added sulfate ions and chloride ions.

9. The process according to claim 1 wherein the acidic aqueous composition is free from added magnesium ions, nickel ions and zinc ions.

10. The process according to claim 1 wherein the zirconium-pretreated metal-based substrate surfaces are zirconium-pretreated steel substrate surfaces or zirconium-pretreated aluminum substrate surfaces or zirconium-pretreated aluminum alloy substrate surfaces.

11. The process according to claim 1 wherein the treating according to step ii. is by spraying the acidic aqueous composition onto the zirconium-pretreated metal-based substrate surfaces at a temperature of between 20 to 25° C.

12. The process according to claim 1 wherein the zirconium-pretreated metal-based substrate surfaces are derived by step i1, treating the metal-based substrate surfaces with an aqueous chromium ion-free composition comprising hexafluorozirconate ions to obtain said zirconium-pretreated metal-based substrate surfaces prior to step ii.

13. The process according to claim 12 wherein the aqueous chromium ion-free composition according to step i1 has a pH of between 4.0 and 5.0 and a concentration of hexafluorozirconate ions between 100 and 5,000 mg/L.

Assignees

• Atotech Deutschland Gmbh

Inventors

• Rousseau Agnes
• Taylor Stephen

Classifications

• C23C22/73

  characterised by the process · CPC title

• C23C2222/10

  Use of solutions containing trivalent chromium but free of hexavalent chromium · CPC title

• C23C22/83

  Chemical after-treatment · CPC title

• C23C22/34 Primary

  containing fluorides or complex fluorides · CPC title

• C23C22/80

  with solutions containing titanium or zirconium compounds · CPC title