Composition For The Anticorrosive Pretreatment And Cleaning Of Metal Surfaces In One Process Step

Abstract

The invention relates to a process for anticorrosive pretreatment of metal surfaces of components which at least partly also have surfaces of iron, wherein acidic aqueous compositions containing water-soluble compounds of both the element Zr and the element Si are used and the compositions can be given a cleaning effect by the addition of surface-active substances, so that metal surfaces soiled with oils and drawing greases likewise can be successfully anticorrosively pretreated in the inventive process in one process step, wherein the invention also comprises an acidic aqueous composition especially suitable such that components that are formed from flat products and that at least also have surfaces of iron can be cleaned and provided with an anticorrosion coating in one process step by means of said composition, said anticorrosion coating being easy to paint over.

What is claimed is: 
     
         1 . A process for the anticorrosive pretreatment of metal surfaces of components, comprising bringing the components into contact with an acidic aqueous composition containing
 a) at least 0.10mmol/kg of water-soluble compounds of the element Zr, and   b) a quantity of water-soluble compounds of the element Si, with quantity calculated as Si, which also represent a source of free fluoride, and   c) optionally at least one surface-active substance;   
       wherein the metal surfaces of the components are at least partially formed from surfaces consisting of the metal iron. 
     
     
         2 . The process according to  claim 1 , wherein the acidic aqueous composition has a molar ratio of water-soluble compounds of the element Zr to water-soluble compounds of the element Si of less than 5.0 but greater than 0.5, based on the respective elements. 
     
     
         3 . The process according to  claim 1 , wherein the acidic aqueous composition contains at least 0.20 mmol/kg and no more than 10.0 mmol/kg, of the water-soluble compounds of the element Zr. 
     
     
         4 . The process according to  claim 1 , wherein the water-soluble compounds of the element Zr are selected from ammonium zirconium carbonate and/or from fluoro acids and their water-soluble salts. 
     
     
         5 . The process according to  claim 1 , wherein the water-soluble compounds of the element Si, which also represent a source of free fluoride, are selected from fluoro complexes. 
     
     
         6 . The process according to  claim 1 , wherein the acidic aqueous composition additionally contains magnesium and/or calcium ions. 
     
     
         7 . The process according to  claim 1 , wherein free fluoride is present in the acidic aqueous composition in an amount of at least 5 mg/kg. 
     
     
         8 . The process according to  claim 1 , wherein c) the at least one surface-active substance is present in the acidic aqueous composition and comprises at least one nonionic surfactant. 
     
     
         9 . The process according to  claim 8 , wherein the acidic aqueous composition additionally contains a hydrotrope. 
     
     
         10 . The process according to  claim 1 , wherein the acidic aqueous composition has a pH of less than 6.0 and greater than 3.5. 
     
     
         11 . The process according to  claim 1 , wherein the acidic aqueous composition contains a total of less than 100 mg/kg of organosilanes having at least one hydrolyzable functional group, in each case calculated as Si. 
     
     
         12 . The process according to  claim 1 , wherein the acidic aqueous composition contains a total of less than 100 mg/kg of phosphates dissolved in water, calculated as PO 4 . 
     
     
         13 . The process according to  claim 1 , wherein a plurality of the components are brought into contact with the acidic aqueous composition in series, either each component of the series or all of the components of the series also having surfaces consisting of the metals zinc and/or aluminum in addition to surfaces consisting of the metal iron. 
     
     
         14 . The process according to  claim 1 , wherein after the metal surfaces of a component have been brought into contact with the acidic aqueous composition, the thus contacted surfaces are immediately thereafter at least partially provided with an organic top coat, with or without an intermediate rinsing and/or drying step. 
     
     
         15 . An acidic aqueous composition containing
 i) at least 0.10 mmol/kg but less than 10 mmol/kg of water-soluble compounds of the element Zr,   ii) at least 0.05 mmol/kg, but less than 10 mmol/kg, of water-soluble compounds of the element Si, calculated as Si, which also constitute a source of free fluoride,   iv) at least one nonionic surfactant,   v) at least one hydrotrope selected from:
 a. alkylsulfonic acids having at least 6 carbon atoms but no more than 10 carbon atoms in the aliphatic functional group; 
 b. benzenesulfonic acids; 
 c. naphthalenesulfonic acids; 
 d. alkylbenzenesulfonic acids having no more than 6 carbon atoms in the aliphatic functional group; and 
 e. water-soluble salts thereof; 
   present in a total amount of at least 0.1 g/kg, calculated as SO 3 ,
 wherein the acidic aqueous composition has a molar ratio of water-soluble compounds of the element Zr to water-soluble compounds of the element Si, based on the respective elements, of less than 5.0 but greater than 0.5. 
   
     
     
         16 . The acidic aqueous composition of  claim 15 , wherein the at least one hydrotrope is selected from p-cumenesulfonic acid and water-soluble salts thereof. 
     
     
         17 . The acidic aqueous composition of  claim 15 , wherein the molar ratio of water-soluble compounds of the element Zr to water-soluble compounds of the element Si is less than 3.0 but greater than 1.0.