Wet on wet method and chrome-free acidic solution for the corrosion control treatment of steel surfaces

Abstract

A process for anticorrosion treatment of bare metal surfaces comprising steel surfaces, wherein the bare metal surfaces are contacted with an acidic aqueous solution of a fluoro complex of at least one element M selected from the group B, Si, Ti, Zr and Hf, at least one further component which is selected from among: a buffer system for the pH range from 2.5 to 5.5, nitrate ions, copper ions, silver ions, vanadium or vanadate ions, bismuth ions, magnesium ions, zinc ions, manganese ions, cobalt ions, nickel ions, tin ions, aromatic carboxylic acids with at least two groups containing donor atoms, or derivatives of such carboxylic acids, and silica particles with an average particle size of below 1 μm; and contains no more than 1 mg/l of an organic polymer with allylamine or vinylamine monomers; the metal surfaces are then rinsed with water and thereafter are coated with a cathodically depositable electro-dipcoating.

1 . A process for anticorrosion treatment of bright metal surfaces, which are at least in part steel surfaces, comprising:
 1) contacting metal surfaces that are not yet coated with an anticorrosion coating, said surfaces comprising at least one steel surface, with an acidic aqueous solution of a fluoro complex of at least one element M selected from the group consisting of B, Si, Ti, Zr and Hf; wherein:   a) the aqueous solution comprises no more than 1 mg/l of an organic polymer with allylamine or vinylamine monomers;   b) the aqueous solution comprises a buffer system for the pH range from 2.5 to 5.5;   c) the aqueous solution comprises at least one component selected from the group consisting of: nitrate ions, copper ions, silver ions, vanadium ions, vanadate ions, bismuth ions, magnesium ions, zinc ions, manganese ions, cobalt ions, nickel ions, tin ions, aromatic carboxylic acids having at least two groups containing donor atoms, derivatives of said carboxylic acids, and silica particles having an average particle size of less than 1 μm;   2) rinsing the metal surfaces after step 1); and   3) coating the metal surfaces with a cathodically depositable electro-dipcoating.   
   
   
       2 . The process according to  claim 1 , wherein the aqueous solution further comprises additional organic polymers that do not contain allylamine or vinylamine monomers, in an amount of less than 2000 mg/l, said polymers having thickening and/or dispersing properties and/or anticorrosion activity. 
   
   
       3 . The process according to  claim 1 , wherein the aqueous solution comprises no more than 1 mg/l of organic polymer. 
   
   
       4 . The process according to  claim 1 , wherein the element M is selected from the group consisting of Si, Ti, Zr and Hf, the aqueous solution contains on average at least 1 fluorine ion per ion of the element M and the fluoro complex is present in an amount such that concentration of the element M is from 1 to 5000 mg/l. 
   
   
       5 . The process according to  claim 1 , wherein the aqueous solution comprises 0.1 to 300 mg/l copper ions and/or silver ions. 
   
   
       6 . The process according to  claim 1 , wherein component c) comprises at least one component selected from the group consisting of hydroxycarboxylic acids, aminocarboxylic acids, nitrocarboxylic acids, carboxylic acids with at least two carboxyl groups, and derivatives of said acids. 
   
   
       7 . The process according to  claim 1 , wherein the aqueous solution comprises 10 to 1000 mg/l of silicon in the form of silica particles with an average particle size of less than 1 μm. 
   
   
       8 . The process according to  claim 1 , wherein after having been brought into contact with the aqueous solution and before being coated with the cathodically depositable electro-dipcoating, the metal surface is not dried. 
   
   
       9 . A process for anticorrosion treatment of bright metal surfaces, which are at least in part steel surfaces, comprising:
 1) contacting metal surfaces that are not yet coated with an anticorrosion coating, said metal surfaces comprising at least one steel surface, with an acidic aqueous solution of a fluoro complex of at least one element M selected from the group consisting of B, Si, Ti, Zr and Hf; wherein:   a) the aqueous solution comprises no more than 1 mg/l of organic polymer;   b) the aqueous solution comprises 10 to 1000 mg/l of silicon in the form of silica particles with an average particle size of less than 1 μm,   c) the aqueous solution comprises at least one component selected from the group consisting of: nitrate ions, copper ions, silver ions, vanadium ions, vanadate ions, bismuth ions, magnesium ions, zinc ions, manganese ions, cobalt ions, nickel ions, tin ions, a buffer system for the pH range from 2.5 to 5.5, aromatic carboxylic acids having at least two groups containing donor atoms, and derivatives of said carboxylic acids;   2) rinsing the metal surfaces after step 1); and   3) coating the metal surfaces with a cathodically depositable electro-dipcoating.   
   
   
       10 . The process according to  claim 9 , wherein the element M is selected from the group consisting of Si, Ti, Zr and Hf and the aqueous solution contains on average at least 1 fluorine ion per ion of the element M. 
   
   
       11 . The process according to  claim 9 , wherein the aqueous solution comprises 0.1 to 300 mg/l copper ions and/or silver ions. 
   
   
       12 . The process according to  claim 11 , wherein the aqueous solution contains a buffer system for the pH range from 2.5 to 5.5. 
   
   
       13 . The process according to  claim 9 , wherein after having been brought into contact with the aqueous solution and before being coated with the cathodically depositable electro-dipcoating, the metal surface is not dried. 
   
   
       14 . An acidic, chromium-free aqueous solution of a fluoro complex of at least one element M selected from the group consisting of B, Si, Ti, Zr and Hf, said aqueous solution having a pH value in the range from 2 to 5.5, and comprising:
 a) a buffer system for the pH range from 2.5 to 5.5,   b) one or more components selected from: copper ions, silver ions, tin ions, bismuth ions, aromatic carboxylic acids with at least two groups containing donor atoms, and derivatives of said carboxylic acids.   
   
   
       15 . The aqueous solution according to  claim 14 , wherein the aqueous solution further comprises silicon in the form of silica particles with an average particle size of less than 1 μm and has an organic polymer content of no more than 1 mg/l; the fluoro complex being present in a quantity such that the concentration of the element M is in a range from 1 to 5000 mg/l. 
   
   
       16 . The aqueous solution according to  claim 14 , wherein the aqueous solution contains no more than 1 mg/l of organic polymers that contain allylamine or vinylamine monomers. 
   
   
       17 . The aqueous solution according to  claim 16 , wherein the aqueous solution further comprises additional organic polymers that do not contain allylamine or vinylamine monomers, in an amount of less than 2000 mg/l, said polymers having thickening and/or dispersing properties and/or anticorrosion activity. 
   
   
       18 . The aqueous solution according to  claim 14 , wherein the aqueous solution additionally contains 10 to 500 mg/l nitroguanidine or 0.1 to 5000 mg/l of nitrate ions. 
   
   
       19 . The process according to  claim 14 , wherein component b) comprises at least one component selected from the group consisting of hydroxycarboxylic acids, aminocarboxylic acids, nitrocarboxylic acids, carboxylic acids with at least two carboxyl groups, and derivatives of said acids. 
   
   
       20 . An acidic, chromium-free aqueous solution of a fluoro complex of at least one element M selected from the group consisting of B, Si, Ti, Zr and Hf, said aqueous solution having a pH value in the range from 2 to 5.5, and comprising:
 a) no more than 1 mg/l of organic polymer;   b) 10 to 1000 mg/l of silicon in the form of silica particles with an average particle size of less than 1 μm; and   c) one or more components selected from among: copper ions, silver ions, tin ions, bismuth ions, buffer systems for the pH range from 2.5 to 5.5, aromatic carboxylic acids with at least two groups containing donor atoms, and derivatives of said carboxylic acids.   
   
   
       21 . The aqueous solution according to  claim 20 , wherein the aqueous solution contains a quantity of fluoro complex such that the concentration of the element M is in the range from 5 to 1000 mg/l. 
   
   
       22 . The aqueous solution according to  claim 20 , wherein the aqueous solution additionally contains 10 to 500 mg/l nitroguanidine or 0.1 to 5000 mg/l of nitrate ions. 
   
   
       23 . The aqueous solution according to  claim 20 , wherein the aqueous solution comprises from 0.1 to 300 mg/l of copper and/or silver ions and 50 to 500 mg/l of silicon in the form of silica particles with an average particle size of below 1 μm. 
   
   
       24 . The aqueous solution according to  claim 20 , wherein the aqueous solution contains on average at least 1 fluorine ion per ion of the element M and, in the fluoro complex, the element M is selected from the group consisting of Si, Ti, Zr and Hf. 
   
   
       25 . The aqueous solution according to  claim 20 , wherein, in the fluoro complex, there are six fluorine ions per ion of the element M and the aqueous solution also contains 1 to 1000 mg/l of fluoride ions which are not attached to the element M. 
   
   
       26 . An aqueous concentrate which, on dilution with water by a factor of between 10 and 100, and optional adjustment of pH, gives rise to an aqueous solution according to  claim 20 . 
   
   
       27 . A process for the anticorrosion treatment of bright metal surfaces, wherein the metal surfaces are brought into contact with an aqueous solution according to  claim 20 .