Conversion coating solutions and methods of use therefor

Abstract

A zirconium conversion coating solution may comprise an aqueous solution; non-fluoride containing zirconium compound; sulfuric acid; and an organic acid. A method of coating a substrate may comprise exposing the substrate to the zirconium conversion coating solution to form a coated substrate.

1 . A zirconium conversion coating solution comprising:
 an aqueous solution;   a non-fluoride containing zirconium compound;   sulfuric acid; and   an organic acid.   
     
     
         2 . The zirconium conversion coating solution of  claim 1 , wherein the non-fluoride containing zirconium compound comprises a zirconium carboxylate. 
     
     
         3 . The zirconium conversion coating solution of  claim 1 , wherein the non-fluoride containing zirconium compound comprises zirconium acetate. 
     
     
         4 . The zirconium conversion coating solution of  claim 1 , wherein the organic acid comprises a carboxylic acid, a hydroxycarboxylic acid, or both. 
     
     
         5 . The zirconium conversion coating solution of  claim 1 , further comprising an accelerator comprising a nitroaromatic sulfonate salt, hydroxylammonium sulfate, ammonium dimolybdate, hydroxylamine hydrochloride, or combinations thereof. 
     
     
         6 . The zirconium conversion coating solution of  claim 1 , further comprising a nonionic surfactant. 
     
     
         7 . The zirconium conversion coating solution of  claim 1 , wherein the nonionic surfactant comprises an ethoxylated surfactant, a propoxylated surfactant, or both. 
     
     
         8 . The zirconium conversion coating solution of  claim 7 , further comprising:
 an accelerator comprising sodium nitrobenzene sulfonate;   a nonionic surfactant comprising an ethoxylated copolymer surfactant, a propoxylated copolymer surfactant, an alcoxylated alcohol, an ethoxylated alcohol, or combinations thereof, and wherein:
 the non-fluoride containing zirconium compound comprise zirconium acetate, and 
 the organic acid comprises lactic acid. 
   
     
     
         9 . The zirconium conversion coating solution of  claim 1 , comprising:
 from 0.5 wt. % to 8 wt. % zirconium compound;   from 0.5 wt. % to 10 wt. % sulfuric acid;   from 0.5 wt. % to 8 wt. % organic acid; and   the balance aqueous solution.   
     
     
         10 . The zirconium conversion coating solution of  claim 9 , further comprising:
 from 0.1 to 5 wt. % nonionic surfactant; and   from 0.5 wt. % to 5 wt. % accelerator.   
     
     
         11 . A method of coating a substrate comprising exposing the substrate to a zirconium conversion coating solution to form a coated substrate, wherein the zirconium conversion coating solution comprises:
 an aqueous solution;   a non-fluoride containing zirconium compound;   sulfuric acid; and   an organic acid.   
     
     
         12 . The method of  claim 11 , further comprising exposing the coated substrate to a paint, thereby forming a painted substrate. 
     
     
         13 . The method of  claim 11 , wherein the substrate comprises steel, galvanized steel, aluminum, magnesium, or combinations thereof. 
     
     
         14 . The method of  claim 11 , wherein the zirconium conversion coating solution further comprises:
 an accelerator; and   a nonionic surfactant.   
     
     
         15 . The method of  claim 14 , wherein:
 the accelerator comprises a nitroaromatic sulfonate salt, hydroxylammonium sulfate, ammonium dimolybdate, hydroxylamine hydrochloride, or combinations thereof; and   the nonionic surfactant comprises an ethoxylated copolymer surfactant, a propoxylated copolymer surfactant, an alcoxylated alcohol, an ethoxylated alcohol, or combinations thereof.   
     
     
         16 . The method of  claim 11 , wherein the organic acid comprises a carboxylic acid, a hydroxycarboxylic acid, or both. 
     
     
         17 . The method of  claim 11 , wherein the zirconium conversion coating solution further comprises:
 an accelerator comprising sodium nitrobenzene sulfonate;   a nonionic surfactant comprising an ethoxylated copolymer surfactant, a propoxylated copolymer surfactant, or both, and wherein:
 the non-fluoride containing zirconium compound comprises zirconium acetate, and 
 the organic acid comprises lactic acid. 
   
     
     
         18 . The method of  claim 17 , wherein the zirconium conversion coating solution comprises:
 from 0.5 wt. % to 8 wt. % non-fluoride containing zirconium compound;   from 0.5 wt. % to 10 wt. % sulfuric acid;   from 0.5 wt. % to 8 wt. % organic acid;   from 0.1 to 5 wt. % nonionic surfactant;   from 0.5 wt. % to 5 wt. % accelerator; and   the balance aqueous solution.   
     
     
         19 . The method of  claim 11 , wherein the non-fluoride containing zirconium compound comprises a zirconium carboxylate. 
     
     
         20 . The method of  claim 11 , wherein the non-fluoride containing zirconium compound comprises zirconium acetate.