Method for the creation of highly lustrous surfaceson aluminum workpieces

Abstract

Disclosed is a method for creating a highly lustrous surface on a workpiece which is made of aluminum or aluminum alloy and has a peak-to-valley height of less than 5 m. Said method comprises the following successive steps: a) the surface is mechanically polished in one or several successive polishing steps by means of a polishing means containing small, hard, sharp-edged particles, whereupon the mechanically polished surface is cleaned of polishing residues; b) a colorless and transparent conversion solution is applied to the mechanically polished, cleaned surface, whereupon the conversion solution is dried so as to form a conversion layer; c) a layer of clear lacquer which can be hardened and is based on inorganic or organic coating materials is applied to the surface that is provided with a conversion layer; d) the clear lacquer that has been applied to the surface is hardened.

1 . A method for the creation of a highly lustrous surface on an aluminum or aluminum-alloy workpiece having a peak-to-valley height of less than 5 μm, characterized by the following successive steps: 
 a) the surface is mechanically treated by polishing in one or more successive polishing stages by means of a polishing agent containing small, hard, sharp-edged particles, in which polishing stages the particles of the polishing agent used in a subsequent polishing stage have a smaller average particle diameter than the particles of the polishing agent used in a preceding polishing stage, the particles of the polishing agent used in the last polishing stage having an average particle diameter of smaller than 1 μm, after which the mechanically treated surface is cleaned of polishing residues;    b) a colorless and transparent conversion solution is applied on the mechanically treated, cleaned surface, after which the conversion solution is dried to form a conversion layer;    c) a layer of curable clear lacquer based on inorganic or organic coating substances is applied onto the surface provided with a conversion layer;    d) the clear lacquer applied onto the surface is cured.    
   
   
       2 . A method according to  claim 1 , characterized in that the polishing agent is a paste containing particles of diamond, silicon carbide (SiC) or corundum (Al 2 O 3 ).  
   
   
       3 . A method according to  claim 1 , characterized in that the conversion layer contains a titanium/zirconium compound with an organic polymer in aqueous solution.  
   
   
       4 . A method according to  claim 1 , characterized in that the clear lacquer based on organic coating substances is a pure acrylate resin.  
   
   
       5 . A method according to  claim 1 , characterized in that the clear lacquer is applied electrostatically or by vapor deposition onto the surface.  
   
   
       6 . The use of the method according to  claim 1  for the creation of a highly lustrous surface on an aluminum-alloy workpiece, wherein the aluminum alloy has an iron content of higher than 0.04 weight percent.  
   
   
       7 . The use of the method according to  claim 1  for the creation of a highly lustrous surface on an aluminum-alloy workpiece, wherein the aluminum alloy has an iron content of higher than 0.08 weight percent.