Coated substrate having corrosion resistant coating

Abstract

A coated substrate made by a method that 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.

1 . A coated substrate made by a method comprising:
 pre-treating a metal substrate such that a surface of the metal substrate is de-oxidized, wherein the metal substrate is selected from the group consisting of aluminum, zinc, cadmium, copper, silver, magnesium, tin, iron, aluminum based alloys, zinc based alloys, cadmium based alloys, copper based alloys, silver based alloys, magnesium based alloys, iron based alloys, and tin based alloys;   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 coated substrate 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 coated substrate 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 coated substrate of  claim 1 , wherein the gaseous atmosphere has a relative humidity of over fifty percent. 
     
     
         5 . The coated substrate of  claim 1 , wherein the metal substrate is post-treated with 0.3 wt % to 3.5 wt % hydrogen peroxide solution. 
     
     
         6 . The coated substrate of  claim 5 , wherein the metal substrate is post-treated with 1.0 wt % to 2.5 wt % hydrogen peroxide solution. 
     
     
         7 . A coated substrate made by the 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.