Stable, thin-film organic passivates

Abstract

An aqueous liquid passivate composition for treating metal surfaces having dispersed therein solid particles which result in a transparent or translucent, preferably colorless, corrosion resistant coating, upon drying of the aqueous liquid passivate composition, the coating providing better resistance to heating by solar energy than the untreated metal surface at lower coating thicknesses than paint.

1 . A composition useful for passivating a metal surface, said composition comprising water and: 
 (A) dispersed solid particles of metal and/or metalloid oxide, desirably the metal and/or metalloid oxide is a powder the particles preferably having a mean particle size of less or equal to 100 nm, and    (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A);    (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin;    and, optionally, one or more of the following components:    (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C);    (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D);    (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E);    (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F);    (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G);    (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and    (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I);    wherein said composition comprises less than 0.04 wt % chromium and dries to a transparent or translucent coating having an emittance of at least 0.60 and a reflectance of at least 0.60.    
   
   
       2 . The composition of  claim 1 , wherein the total concentration of the complex fluoride is at least 0.5 g/L and is not more than 100 g/L.  
   
   
       3 . The composition of  claim 1 , wherein the at least one complex fluoride is a titanium and/or zirconium complex fluoride.  
   
   
       4 . The composition of  claim 1 , wherein said composition is essentially free of chromium, the resin comprises a non-ionic or non-ionically stabilized acrylic and/or acrylic copolymer resin in dispersed form, said composition comprising at least one pH adjusting component.  
   
   
       5 . The composition of  claim 1 , wherein the pH of the composition is within a range of from about 1 to about 5 and the composition is storage stable at 100 deg. F. for at least 3 months.  
   
   
       6 . The composition of  claim 1 , comprising at least one component that comprises vanadium.  
   
   
       7 . The composition of  claim 1 , comprising at least one wax, selected from the group of waxes stable in strong acidic solutions having an average particle size less than about 1 micron and a melting point of from about 50 to about 175 degrees C.  
   
   
       8 . The composition of  claim 1 , containing: 
 (A) 25-75 weight % of at least one inorganic oxide in dispersed form, the particles preferably having a mean particle size of less than 100 nm;    (B) 0.05-5 weight % of at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti and/or Zr;    (C) 10-50 weight % of a non-ionic or non-ionically stabilized resin in dispersed form selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof;    (D) optionally, dissolved phosphate anions;    (E) 0.1 to 7 weight % of at least one component comprising vanadium;    (F) 0.05-20 weight % of at least one wax in dispersed form;    (G) and optionally, at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component; said composition comprising less than 0.04 wt % chromium.    
   
   
       9 . A process of treating a ferriferous, aluminiferous or zinciferous metal substrate comprising: 
 optionally, cleaning a surface of said metal substrate to be passivated;    contacting the metal substrate surface to be passivated with a passivating composition for a time sufficient to form a coating on said metal surface, wherein the passivating composition comprises water and: 
 (A) at least one inorganic oxide in dispersed form, the particles preferably having a mean particle size of less than 100 nm;  
 (B) at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti and/or Zr;  
 (C) a non-ionic or non-ionically stabilized resin in dispersed form selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof;  
 (D) optionally, dissolved phosphate anions;  
 (E) optionally, at least one component comprising vanadium;  
 (F) optionally, at least one wax in dispersed form;  
 (G) and optionally, at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component;  
 said composition comprising less than 0.04 wt % chromium; and  
   drying to form a transparent or translucent passivate coating having an emittance of 0.60 and a reflectance of 0.60, on the metal surface.    
   
   
       10 . The process of  claim 14  further comprising the step of coating the metal substrate with a dissimilar metal, thereby creating a metal substrate surface to be passivated, prior to contacting with the passivating composition.  
   
   
       11 . A uniform and stable liquid composition of matter comprising water and the following components: 
 (A) dispersed solid particles of metal and/or metalloid oxide having a mean particle size of less or equal to 100 nm, and    (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A);    (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin;    and, optionally, one or more of the following components:    (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C);    (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D);    (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E);    (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F);    (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G);    (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and    (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I);    wherein said composition dries to a transparent or translucent coating having an emittance of at least 0.60 and a reflectance of at least 0.60.    
   
   
       12 . The composition of  claim 11 , wherein the dispersed solid particles of metal and/or metalloid oxide are selected from oxides of Ti, Zn, Zr, Sb, Al, Hf, and V.  
   
   
       13 . The composition of  claim 11 , wherein the dispersed solid particles of metal and/or metalloid oxide are present in an amount of about 10.0 to about 80.0 weight %.  
   
   
       14 . The composition of  claim 11 , wherein the dispersed solid particles of metal and/or metalloid oxide are selected such that the as-dried coating a clear, colorless coating after not more than 60 days.  
   
   
       15 . The composition of  claim 11 , wherein the dispersed solid particles of metal and/or metalloid oxide are selected such that the coating has emittance of at least 0.60 at wavelengths of about 250 to about 2500 nm.  
   
   
       16 . The composition of  claim 11 , wherein the dispersed solid particles of metal and/or metalloid oxide have a mean particle size range from about 1 to about 50 nanometers.  
   
   
       17 . The composition of  claim 11 , wherein the dispersed solid particles of metal and/or metalloid oxide have a mean particle size range from about 5 to about 35 nanometers.  
   
   
       18 . The composition of  claim 11 , wherein the dispersed solid particles of metal oxide are selected from oxides of Ti, Zn, Zr, Sb, Al, Hf, and V.  
   
   
       19 . A process of treating a ferriferous, aluminiferous or zinciferous metal substrate comprising: 
 optionally, cleaning a surface of said metal substrate to be passivated;    contacting the metal substrate surface to be passivated with a passivating composition for a time sufficient to form a coating on said metal surface, wherein the passivating composition comprises water and: 
 (A) dispersed solid particles of metal and/or metalloid oxide having a mean particle size of less or equal to 100 nm, and  
 (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A);  
 (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin;  
   and, optionally, one or more of the following components: 
 (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C);  
 (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D);  
 (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E);  
 (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F);  
 (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G);  
 (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and  
 (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I);  
   drying to form a passivate coating having an emittance of 0.60 and a reflectance of 0.60 and a thickness of 12 microns or less, on the metal surface.    
   
   
       20 . The process of  claim 19  further comprising the step of coating the metal substrate with a dissimilar metal, thereby creating a metal substrate surface to be passivated, prior to contacting with the passivating composition.