Method for making corrosion resistant coating

Patent metadata

Field	Value
Publication number	US-10294570-B2
Application number	US-201615095926-A
Country	US
Kind code	B2
Filing date	Apr 11, 2016
Priority date	Apr 11, 2016
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A method for making an environmentally-safe chromium based corrosion resistant coating includes pre-treating a metal substrate, immersing the metal substrate in a trivalent chromium bath which does not contain hexavalent chromium, post-treating the coated metal substrate with an oxidizer, and curing the coated metal substrate in a controlled environment.

First claim

The invention claimed is:

1. A method comprising:
pre-treating a metal substrate such that a surface of the metal substrate is de-oxidized;
immersing the metal substrate in a coating solution to produce a chromium based coating on the metal substrate, wherein the coating solution comprises a trivalent chromium compound and a fluoride compound, but does not contain hexavalent chromium;
removing the coated metal substrate from the coating solution;
curing the chromium based coating in a controlled environment containing a gaseous atmosphere to produce a hexavalent chromium enriched corrosion resistant coating on the metal substrate;
post-treating the coated metal substrate with an oxidizer after removing the coated metal substrate from the coating solution, but before curing the coating; and
exposing the coated metal substrate to ozone in the controlled environment.

2. The method of claim 1 , wherein exposing the coated metal substrate to ozone in the controlled environment comprises exposing the coated metal substrate to 1 ppm ozone for one hour.

3. The method of claim 1 , wherein exposing the coated metal substrate to ozone in the controlled environment comprises exposing the coated metal substrate to 0.1 ppm ozone for between four and twenty-four hours.

4. The method of claim 1 , wherein the gaseous atmosphere has a relative humidity of over fifty percent.

5. The method of claim 1 , wherein the metal substrate is post-treated with 0.3 wt % to 3.5 wt % hydrogen peroxide solution.

6. The method of claim 5 , wherein the metal substrate is post-treated with 1.0 wt % to 2.5 wt % hydrogen peroxide solution.

7. A method comprising:
pre-treating a metal substrate such that a surface of the metal substrate is de-oxidized;
immersing the metal substrate in a coating solution to produce a chromium based coating on the metal substrate, wherein the coating solution comprises a trivalent chromium compound and a fluoride compound, but does not contain hexavalent chromium;
removing the coated metal substrate from the coating solution;
curing the chromium based coating in a controlled environment containing a gaseous atmosphere to produce a hexavalent chromium enriched corrosion resistant coating on the metal substrate, wherein the gaseous atmosphere has a relative humidity of over fifty percent;
post-treating the coated metal substrate with an oxidizer after removing the coated metal substrate from the coating solution, but before curing the coating, wherein the metal substrate is post-treated with 0.3 wt % to 3.5 wt % hydrogen peroxide solution; and
exposing the coated metal substrate to ozone in the controlled environment.

Assignees

• Hamilton Sundstrand Corp

Inventors

• Jaworowski Mark R
• Smith Blair A
• Zafiris Georgios S
• Zhang Weilong
• Kryzman Michael A
• Hugener-Campbell Treese
• Van Hassel Bart Antonie

Classifications

• C23C22/78

  Pretreatment of the material to be coated · CPC title

• C23C22/82

  After-treatment · CPC title

• C23C22/83

  Chemical after-treatment · CPC title

• C23C22/34 Primary

  containing fluorides or complex fluorides · CPC title

• C23C2222/10

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