Passivation composition and process for zinciferous and aluminiferous surfaces

Abstract

In at least one embodiment, the present invention relates to a process for the temporary anti-corrosive treatment of a metal surface that consist predominantly of aluminum and/or zinc, said process comprising a) placing the surface of the metal in contact with an anti-corrosive composition comprising 2.0-400 g/L phosphate ions, 0.5-400 g/L fluorometallate ions, and having a pH of between 1.0-4.0, for a time period of between 0.1-200 seconds, b) drying the anti-corrosive treatment composition on the metal surface to form a primary passivating coating on the metal surface, c) removing the primary passivating coating from the metal surface, and d) conversion coating the metal surface. In certain embodiments, the phosphate solution comprises phosphoric acid and the fluorometallate solution comprises hexafluorotitanic acid.

1 . A method for the temporary anti-corrosive treatment of a metal surface that consist predominantly of aluminum and/or zinc, said process comprising: 
 a) placing the surface of the metal in contact with an anti-corrosive composition comprising 2.0-400 g/L phosphate ions, 0.5-400 g/L fluorometallate ions, and having a pH of between 1.0-4.0, for a time period of between 0.1-200 seconds;    b) drying the anti-corrosive treatment composition on the metal surface to form a primary passivating coating on the metal surface;    c) removing the primary passivating coating from the metal surface; and    d) conversion coating the metal surface.    
     
     
         2 . The method of  claim 1  wherein the ratio of fluorometallate anions and phosphate ions is 0.10:1.0 to 5.0:1.0.  
     
     
         3 . The method of  claim 1  wherein the phosphate ions are provided in a 75% by weight phosphate solution, based on the total weight of the phosphate solution, and the fluorometallate ions are provided in a 50% by weight fluorometallate solution, based on the total weight of the fluorometallate solution.  
     
     
         4 . The method of  claim 3  wherein the phosphate solution is present in the composition in an amount of 25-65 wt. % and the fluorometallate solution is present in the composition in an amount of 35-75 wt. %, based on the total weight of the composition.  
     
     
         5 . The method of  claim 4  further comprising water present in an amount of 2 to 50 wt. %, based on the total weight of the composition.  
     
     
         6 . The method of  claim 3  wherein the phosphate solution comprises phosphoric acid and the fluorometallate solution comprises hexafluorotitanic acid.  
     
     
         7 . The method of  claim 6  wherein the phosphoric acid is present in the composition in an amount of 1.0-15.0 wt. %, based on the total weight of the composition, and the hexafluorotitanic acid is present in an amount of 1.0-20.0 wt. %, based on the total weight of the composition, and the composition further comprising water present in an amount of 45-98 wt. %, based on the total weight of the composition.  
     
     
         8 . The method of  claim 1  wherein the metal surface comprises steel treated with a galvanic coating comprising aluminum, zinc and silicon.  
     
     
         9 . The method of  claim 1  wherein the metal surface comprises steel treated with a galvanic coating comprising 55% aluminum, 43.5% zinc and 1.5% silicon.  
     
     
         10 . The method of  claim 1  wherein the temperature of the composition during step a) is 15-66° C.  
     
     
         11 . The method of  claim 1  wherein the primary passivating coating method surface is stored after step b) and prior to step c).  
     
     
         12 . The method of  claim 1  wherein the removal of step c) takes place by exposing the primary passivating coating to an alkaline solution.  
     
     
         13 . A chromium-free, anti-corrosive composition for temporarily passivating metal surfaces consisting predominantly of aluminum and/or zinc, said composition comprising: 
 2.0-400 g/L phosphate ions; and    0.5-400 g/L fluorometallate anions;    the composition having a pH of 1.0-4.0.    
     
     
         14 . The composition of  claim 13  wherein the ratio of fluorometallate anions and phosphate ions is 0.10:1.0 to 5.0:1.0.  
     
     
         15 . The composition of  claim 13  wherein the phosphate ions are provided in a 75% by weight phosphate solution, based on the total weight of the phosphate solution, and the fluorometallate ions are provided in a 50% by weight fluorometallate solution, based on the total weight of the fluorometallate solution.  
     
     
         16 . The composition of  claim 15  wherein the phosphate solution is present in the composition in an amount of 25-65 wt. % and the fluorometallate solution is present in the composition in an amount of 35-75 wt. %, based on the total weight of the composition.  
     
     
         17 . The composition of  claim 16  further comprising water present in an amount of 2 to 50 wt. %, based on the total weight of the composition.  
     
     
         18 . The composition of  claim 15  wherein the phosphate solution comprises phosphoric acid and the fluorometallate solution comprises hexafluorotitanic acid.  
     
     
         19 . The composition of  claim 18  wherein the phosphoric acid is present in the composition in an amount of 1.0-15.0 wt. %, based on the total weight of the composition, and the hexafluorotitanic acid is present in an amount of 1.0-20.0 wt. %, based on the total weight of the composition, and the composition further comprising water present in an amount of 45-98 wt. %, based on the total weight of the composition.  
     
     
         20 . The composition of  claim 19  further comprising a polymer solution comprising a polymer comprising the Mannich adduct of polyhydroxystyrene with N-methylglucamine.  
     
     
         21 . The composition of  claim 20  wherein the polymer solution further comprises an acid selected from the group consisting of fluorotitanic acid and fluorozirconic acid.