Corrosion resistant chromium free conversion coatings

Abstract

Process for treating metal such as aluminum and its alloys to prevent corrosion which comprises coating the metal with a chromium-free conversion composition containing effective amounts of metal fluorozirconates and carboxylic metal salts.

The invention claimed: 
     
         1 . A process for treating metal surfaces to protect the metal from corrosion which comprises coating the metal with a chromium-free conversion coating containing from about 4 to 8 grams of a metal fluorozirconate per liter of the chromium-free conversion coating and from about 0.5 to 5.0 grams of at least one carboxylic metal salt per liter of the chromium-free conversion coating. 
     
     
         2 . The process of  claim 1 , wherein at least one of the carboxylic metal salts has an anion or cation different from the other carboxylic metal salts. 
     
     
         3 . The process of  claim 2 , wherein the cation of the carboxylic metal salt is a metal selected from Group II of the Periodic Table. 
     
     
         4 . The process of  claim 2 , wherein the anion of the carboxylic metal salt is selected from the group consisting of oxalate, tartrate, succinate, adipate, phthalate, mellitate and trimellilate. 
     
     
         5 . The process of  claim 4 , wherein one of the carboxylic metal salts is a metal succinate. 
     
     
         6 . The process of  claim 4 , wherein one of the carboxylic metal salts is a metal oxalate. 
     
     
         7 . The process of  claim 4 , wherein one of the carboxylic metal salts is a metal phthalate. 
     
     
         8 . The process of  claim 4 , wherein the metal is selected from the Periodic Table. 
     
     
         9 . The process of  claim 4 , wherein the metal is selected from Group II of the Period Table. 
     
     
         10 . The process of  claim 1 , wherein the carboxylic metal salt is a polycarboxylic metal salt. 
     
     
         11 . The process of  claim 10 , wherein at least one polycarboxylic metal salt has a cation different from the other carboxylic metal salts.