Sheet steel with a conversion coating, method of producing conversion-coated sheet steel and treatment agent for application of a conversion coating on sheet steel

Abstract

A sheet steel, in particular strip-shaped blackplate, with a conversion coating which is prepared from components dissolved in water. The components are selected from the group of i) hexafluorotitanate, ii) zinc phosphate, iii) phosphoric acid, iv) a mixture of any of i) to iii), provided that the components i), ii) and iii) do not contain any organic ingredients.

What is claimed is: 
     
         1 . A sheet steel with a conversion coating on at least one surface of the sheet steel, wherein the conversion coating contains at least one of the following components:
 i) hexafluorotitanate,   ii) zinc phosphate and/or iron phosphate,   iii) phosphoric acid,   provided that the components i), ii) and iii) do not contain any organic ingredients.   
     
     
         2 . The sheet steel of  claim 1 , wherein the conversion coating consists of one of the following components or a mixture of these components:
 i) hexafluorotitanate,   ii) zinc phosphate and/or iron phosphate,   iii) phosphoric acid,   provided that the components i), ii) and iii) do not contain any organic ingredients.   
     
     
         3 . The sheet steel of  claim 1 , wherein an organic lacquer and/or a plastic coating is applied to the conversion coating. 
     
     
         4 . The sheet steel of  claim 1 , wherein the conversion coating contains phosphate ions. 
     
     
         5 . The sheet steel of  claim 1 , wherein the coating weight of the hexafluorotitanate in the conversion coating, relative to titanium, is in the range of 1 mg/m 2  to 50 mg/m 2 . 
     
     
         6 . The sheet steel of  claim 1 , wherein the coating weight of the phosphate in the conversion coating, relative to phosphate ions, is in the range of 10 mg/m 2  to 1000 mg/m 2 . 
     
     
         7 . A method of producing a conversion-coated sheet steel, comprising the following steps:
 a) having available a sheet steel, in particular in the form of a steel strip;   b) cathodic degreasing of at least one surface of the sheet steel;   c) application of a wet film of a conversion coating to the degreased surface of the sheet steel, with the wet film of the conversion coating being prepared from components dissolved in water and with the components being selected from the group of:
 i) hexafluorotitanate, 
 ii) zinc phosphate and/or iron phosphate, 
 iii) phosphoric acid, and 
 iv) a mixture of any one of i) to iii), 
   provided that the components do not contain any organic substances;   d) drying of the wet film of the conversion coating.   
     
     
         8 . The method of  claim 7 , wherein an organic lacquer and/or a plastic coating is applied to the dried conversion coating. 
     
     
         9 . The method of  claim 7 , wherein, after cathodic degreasing, the degreased surface of the sheet steel is anodically polarized in an alkaline electrolyte. 
     
     
         10 . A treatment agent for application of a conversion coating to sheet steel, wherein the treatment agent contains water and at least one component selected from the group of
 i) hexafluorotitanate,   ii) zinc phosphate and/or iron phosphate,   iii) phosphoric acid and   iv) a mixture of any one of i) to iii),   provided that the components i), ii) and iii) are free of organic ingredients.   
     
     
         11 . The treatment agent of  claim 10 , wherein the treatment agent consists of water and a mixture of hexafluorotitanate, zinc phosphate and/or iron phosphate and phosphoric acid. 
     
     
         12 . The treatment agent of  claim 10 , wherein the treatment agent consists of water and one of the following components or a mixture of these components:
 i) hexafluorotitanate,   ii) zinc phosphate and/or iron phosphate,   iii) phosphoric acid,   provided that the components i), ii) and iii) do not contain any organic ingredients.   
     
     
         13 . The sheet steel of  claim 5 , wherein the coating weight of the hexafluorotitanate in the conversion coating, relative to titanium, is in the range of 10 mg/m 2  to 40 mg/m 2 . 
     
     
         14 . The sheet steel of  claim 6 , wherein the coating weight of the phosphate in the conversion coating, relative to phosphate ions, is in the range of 100 mg/m 2  to 400 mg/m 2 .