Method for treating or pre-treating components comprising aluminum surfaces

Abstract

The invention relates to a method for treating or pre-treating parts, profiles, strips, or wires comprising surfaces of aluminium, or alloys containing aluminium optionally in the presence of surfaces consisting of other metals or alloys with an acidic, aqueous solution containing fluoride and phosphate. Said method is characterised in that the fluoride is present at least partially as a free fluoride in the solution and that in the bath of phosphating solution, the content of free fluoride is maintained within a concentration range of between 5 and 500 mg/l F free and that of aluminium is maintained within a concentration range that is less than or equal to 100 mg/l Al ions (including complexed Al). To achieve this, increases in the aluminium content are reduced to contents of less than or equal to 100 mg/l Al ions in the bath, using a precipitation container outside the phosphating bath by circulating the phosphating solution from the phosphating bath to the precipitation container and vice versa.

1 . Method for the treatment or pretreatment of parts, sections, strips or wires with surfaces of aluminium or of alloys containing aluminium—if applicable in the presence of surfaces of further metals or alloys—with an acid aqueous solution containing fluoride and phosphate, characterised in that the fluoride is at least partly present in the solution as free fluoride, and in that, in the bath of the phosphatizing solution, 
 the free-fluoride content is maintained at a concentration in the range from 5 to 500 mg/l F free , and  
 the aluminium content is maintained at a concentration in the range of ≦100 mg/l Al ions (including complex-bound Al)  
 by virtue of the fact that increasing aluminium contents, in a precipitation tank outside the phosphatizing bath, are decreased to contents ≦100 mg/l Al ions in the bath by circulating the phosphatizing solution from the phosphatizing bath to the precipitation tank and back.  
 
     
     
         2 . Method according to  claim 1 , modified in that, in a separate zone of the phosphatizing bath, increasing aluminium contents in the phosphatizing solution are decreased to contents ≦100 mg/l Al ions.  
     
     
         3 . Method according to  claim 1  or  2 , characterised in that, in the tank or in the separate zone of the bath, aluminium is precipitated in the phosphatizing solution by adding alkali ions, fluoride complexes and/or fluoride ions, in particular by means of Na or K ions or by means of at least one easily dissociating fluoride such as, for example, NaF, NH 4 F, NaHF 2  or KF.  
     
     
         4 . Method according to one of the preceding claims, characterised in that the alkali ion content in the bath is maintained at a concentration in the range from 1 to 20 g/l.  
     
     
         5 . Method according to one of the preceding claims, characterised in that the free-fluoride concentration in the precipitation tank or in the separate zone of the bath container is 5 to 500 mg/l free fluoride.  
     
     
         6 . Method according to one of the preceding claims, characterised in that the dwell time of the phosphatizing solution in the precipitation tank or in the separate precipitation zone is up to 1 h.  
     
     
         7 . Method according to one of the preceding claims, characterised in that, prior to pickling/phosphatizing, the parts, sections, strips and/or wires to be treated or pretreated are cleaned, rinsed and, if appropriate and separately from the rinsing and cleaning stages, brought into contact with an activating solution, for example on the basis of colloidally dispersed titanium phosphate.  
     
     
         8 . Method according to one of the preceding claims, characterised in that, after pickling/phosphatizing, the treated or pretreated parts, sections, strips and/or wires are rinsed and/or passivated, in particular by means of a passivating solution on the basis of a chromate-containing compound, titanium fluoride, zirconium fluoride, silane, self-organizing molecules for example on the basis of phosphonate, a polymer soluble and/or dispersible in solvent, a soluble rare-earth compound—in particular a soluble cerium-containing compound, with the term rare-earth element also including scandium, yttrium and lanthanum.  
     
     
         9 . Method according to one of the preceding claims, characterised in that the treated or pretreated and/or passivated parts, sections, strips and/or wires are dried after pickling/phosphatizing or after passivation.  
     
     
         10 . Method according to one of the preceding claims, characterised in that the precipitation of the aluminium is effected under normal pressure and at a temperature in the range from room temperature to 70° C.  
     
     
         11 . Method according to one of the preceding claims, characterised in that the formation of the conversion or passivation layer is effected under normal pressure and at a temperature from room temperature to 70° C.  
     
     
         12 . Method according to one of the preceding claims, characterised in that the treated or pretreated and/or passivated parts, sections, strips and/or wires are coated with a lacquer, with another kind of organic coating, with a film and/or with an adhesive layer, if applicable printed and if applicable reshaped, where the metal parts coated in this way can in addition be bonded, welded and/or otherwise connected together with other parts.  
     
     
         13 . Use of the products produced in accordance with the method according to  claims 1  to  12  in the automotive industry, in the aeronautical industry, in apparatus and machine construction, in the furniture industry, in the building trade, for household appliances, electrical appliances, measuring instruments, control devices, testing devices, construction elements, housings, panellings, shelf systems, racks, frames, dividers, partitions, trim panels, lighting fixtures, crash barriers, radiator or fence elements as well as small parts, in particular for car body parts or car bodies.