Reduction of chromium waste water in an aluminum conversion coat processing line

Patent metadata

Field	Value
Publication number	US-9683293-B2
Application number	US-201313961096-A
Country	US
Kind code	B2
Filing date	Aug 7, 2013
Priority date	Aug 7, 2013
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

The present disclosure relates generally to the field of conversion coating. More specifically, the present disclosure relates to improved methods for improving efficiency of chromium conversion coat processing lines.

First claim

I claim:

1. A method for reducing the amount of rinse water produced in a chromium-containing conversion coating process comprising the steps of:
preparing a substrate having a substrate surface for immersion into a deoxidizing solution;
immersing the substrate into a chromium-containing deoxidizing solution to deoxidize the substrate surface;
removing the substrate from the deoxidizing solution;
immersing the substrate into a chromium-containing conversion coating solution; and
eliminating production of chromium contaminated rinse water in the chromium-containing conversion coating process;
wherein the substrate is withdrawn from the deoxidizing solution without a rinse step.

2. The method of claim 1 , wherein the substrate comprises an aluminum-containing component.

3. The method of claim 2 , wherein the aluminum-containing component comprises an aluminum alloy.

4. The method of claim 2 , wherein the aluminum-containing component comprises aluminum 2024-T3.

5. The method of claim 1 , wherein the deoxidizing solution comprises chromium ions and an inorganic acid.

6. The method of claim 1 , wherein the conversion coating solution comprises chromium-containing ions in the conversion coating solution.

7. The method of claim 6 , wherein the chromium-containing ions are supplied to the conversion coating solution by a soluble chromium-containing compound.

8. The method of claim 1 , further comprising the step of maintaining the conversion coating solution at a pH ranging from about 1 to about 2.

9. The method of claim 8 , wherein the pH is maintained by adding a base to the conversion coating solution.

10. The method of claim 9 , wherein the base comprises sodium hydroxide.

11. The method of claim 1 , wherein, in the step of immersing the substrate into a chromium-containing conversion coating solution, an amount of deoxidizing solution is transferred into the chromium-containing conversion coating.

12. The method of claim 1 , wherein, in the step of immersing the substrate into a chromium-containing conversion coating solution, said chromium-containing conversion coating solution further comprises a buffer.

13. The method of claim 1 , wherein, in the step of immersing the substrate into a chromium-containing conversion coating solution, said chromium-containing conversion coating solution further comprises a conjugate base of nitric acid.

14. The method of claim 1 , wherein, in the step of immersing the substrate into a chromium-containing conversion coating solution, said chromium-containing conversion coating solution further comprises an amount of ammonium nitrate.

15. The method of claim 1 , wherein, in the step of immersing the substrate into a chromium-containing conversion coating solution, said chromium-containing conversion coating solution further comprises an amount of potassium nitrate.

16. The method of claim 1 , wherein the deoxidizing solution comprises chromium ions and nitric acid.

17. A method for reducing the amount of flowing rinse water produced in a chromium-containing conversion coating process comprising the steps of:
preparing a substrate having a substrate surface for immersion into a deoxidizing solution;
immersing the substrate into a chromium-containing deoxidizing solution to deoxidize the substrate surface;
removing the substrate from the deoxidizing solution;
immersing the substrate into a dead rinse;
removing the substrate from the dead rinse;
immersing the substrate into a chromium-containing conversion coating solution; and
eliminating production of flowing chromium contaminated waste water in the chromium-containing conversion coating process
wherein the substrate is withdrawn from the deoxidizing solution without a rinse step.

18. The method of claim 17 , further comprising the step of maintaining the conversion coating solution at a pH ranging from about 1 to about 2.

19. The method of claim 18 , wherein the pH is maintained by adding a base to the conversion coating solution.

Assignees

• Boeing Co

Inventors

• Lawless Lawrence M

Classifications

• C23C22/37

  containing also hexavalent chromium compounds · CPC title

• C23C22/04 Primary

  containing hexavalent chromium compounds · CPC title

• C23C22/78 Primary

  Pretreatment of the material to be coated · CPC title

• C23C22/73

  characterised by the process · CPC title