Use of rare earth metal salt solutions for sealing of anodized aluminum for corrosion protection and paint adhesion

Abstract

A process for sealing the surface coating formed by anodizing an aluminum or aluminum alloy substrate (for example, aerospace, commercial, and architectural products), the process including the steps of: (a) providing an aluminum or aluminum alloy substrate with a surface coating formed thereon by anodizing the aluminum or aluminum alloy substrate; (b) providing a sealing solution comprising a dilute solution of a rare earth metal salt selected from the group consisting of cerium salts and yttrium salts; and (c) contacting the substrate with the sealing solution for a sufficient amount of time to seal the surface coating on the substrate. Also disclosed is a chemical sealing solution for sealing the surface coating formed by anodizing an aluminum or aluminum alloy substrate, the solution being a dilute solution of a rare earth metal salt selected from the group consisting of cerium salts and yttrium salts.

What is claimed is:  
     
         1 . A process for sealing the surface coating formed by anodizing an aluminum or aluminum alloy substrate, said process comprising the steps of: 
 (a) providing an aluminum or aluminum alloy substrate with a surface coating formed thereon by anodizing said aluminum or aluminum alloy substrate;    (b) providing a sealing solution comprising a dilute solution of a rare earth metal salt selected from the group consisting of cerium salts and yttrium salts; and    (c) contacting said surface coating on said substrate with said sealing solution for a sufficient amount of time to seal said surface coating on said substrate.    
     
     
         2 . The process of  claim 1  wherein said sealing solution comprises a dilute solution of cerium salts.  
     
     
         3 . The process of  claim 1  wherein said sealing solution comprises a dilute solution of yttrium salts.  
     
     
         4 . The process of  claim 1  wherein said sealing solution comprises a dilute solution of a rare earth metal salt selected from the group consisting of cerium nitrate, yttrium sulfate, and cerium sulfate.  
     
     
         5 . The process of  claim 1  wherein the chemical concentration of the dissolved rare earth metal salt in the sealing solution is from about 10 mM to about 350 mM.  
     
     
         6 . The process of  claim 1  wherein the pH of said sealing solution is from about 3.0 to about 9.0.  
     
     
         7 . The process of  claim 1  wherein the immersion time in said sealing solution is from about 10 minutes to about 60 minutes.  
     
     
         8 . The process of  claim 1  wherein the temperature of the sealing solution is from about 60° C. to the boiling temperature of the sealing solution.  
     
     
         9 . A chemical sealing solution for sealing the surface coating formed by anodizing an aluminum or aluminum alloy substrate, said solution comprising a dilute solution of a rare earth metal salt selected from the group consisting of cerium salts and yttrium salts.  
     
     
         10 . The chemical sealing solution of  claim 9  wherein said sealing solution comprises a dilute solution of cerium salts.  
     
     
         11 . The chemical sealing solution of  claim 9  wherein said sealing solution comprises a dilute solution of yttrium salts.  
     
     
         12 . The chemical sealing solution of  claim 9  wherein said sealing solution comprises a dilute solution of a rare earth metal salt selected from the group consisting of cerium nitrate, yttrium sulfate, and cerium sulfate.  
     
     
         13 . The chemical sealing solution of  claim 9  wherein the chemical concentration of the dissolved rare earth metal salt in said sealing solution is from about 10 mM to about 350 mM.  
     
     
         14 . The chemical sealing solution of  claim 9  wherein the pH of said sealing solution is from about 3.0 to about 9.0.  
     
     
         15 . The chemical sealing solution of  claim 9  wherein the temperature of said sealing solution is from about 60° C. to the boiling temperature of the sealing solution.