Pretreatment process for coating of aluminum materials

Abstract

The invention relates to a method for applying electro-deposited metal coatings ( 3 ) upon aluminium or aluminium alloy components ( 1 ). According to said method, the surface ( 4 ) of the component is cleaned in an appropriate solution, in particular a solution of oils, fats, emulsions, pigments, etc. Said surface ( 4 ) is then etched in an appropriate solution, such that a certain quantity of material or near-surface alloy constituents is dissolved. After cleaning and dissolution, water rinsing is carried out. Immediately after the dissolution of the near-surface regions, the surface ( 4 ) of said component ( 1 ) is activated in a solution, containing iron ions, with a sulphate base by the anodic coupling of said component ( 1 ). The functional layer ( 3 ) is then applied by the cathodic coupling of said component ( 1 ), without intermediate rinsing, in the same electrolyte or in a similar or equivalent electrolyte, said functional layer ( 3 ) being made of iron ( 5 ).

1 - 16 . (canceled)  
     
     
         17 . A method of galvanically coating iron on a surface of an aluminum-based substrate, said method comprising: 
 selecting the aluminum component to include an amount of silicon;    cleaning the surface of impurities;    etching the surface to remove material at the surface;    rinsing the surface with water;    immersing the surface in an electrolytic iron sulfate solution; and    first activating the electrolyte by anodically switching the component and then, without rinsing, depositing a functional layer of the iron by cathodic switching of the component.    
     
     
         18 . The method of  claim 17  including selecting FeSO4*7H20 as the electrolytic solution.  
     
     
         19 . The method of  claim 18  wherein the electrolytic solution is maintained at a pH value of between 0.5 and 2.5.  
     
     
         20 . The method of  claim 19  including selecting the amount of silicon in the aluminum-based component to include between 3 and 22% by weight silicon.  
     
     
         21 . The method of  claim 20  wherein the activation of the component in the electrolyte is carried out with an exposure time of between 5 seconds and 5 minutes.  
     
     
         22 . The method of  claim 20  wherein the activation of the component and the deposition of the functional layer is carried out with a DC current density of 2 to 20 A/dm 2 .  
     
     
         23 . The method of  claim 20  wherein the activation of the component is carried out in the solution maintained at a temperature ranging from 20 to 95° C.  
     
     
         24 . The method of  claim 20 , including adding to the electrolytic solution particles of at least one hard material having a particle size of about 0.2 to 5 μm and selected from the group consisting essentially of aluminum oxide, silicon nitride, chromium nitride, chromium nitride, titanium carbide, cubic boron nitride, and diamond particles.  
     
     
         25 . The method of  claim 20 , including adding to the electrolytic solution solid lubricant particles having a particle size of about 0.2 to 5 μm and selected from the group consisting essentially of: hexagonal boron nitride, carbon fluoride, graphite, molybdenum sulfide, Teflon, or microcapsules filled with oil.  
     
     
         26 . The method of  claim 20 , including adding particles of at least one hard material and at least one solid lubricant to the electrolyte.  
     
     
         27 . The method of  claim 20  including adding hypophosphoric acid to the electrolyte.  
     
     
         28 . The method of  claim 27  wherein the hypophosphoric acid comprises H3PO2.  
     
     
         29 . The method of  claim 28  wherein the H3PO2 is 50% H3PO2 and is added in an amount of 0.25 to 5 ml/l of electrolytic solution.  
     
     
         30 . The method of  claim 20  including applying at least one additional layer to the functional layer.  
     
     
         31 . The method of  claim 30  wherein the at least one additional layer is selected from the group consisting essentially of: tin, copper, nickel, chromium, of ceramic or metal ceramic materials, and materials and alloys that have an affinity to iron.  
     
     
         32 . The method of  claim 31  wherein the at least one additional layer is applied by a process selected from the group consisting essentially of: electrochemical, thermal, and PVD or CVD reactive processes.  
     
     
         33 . The method of  claim 20  including selecting a piston as the component.  
     
     
         34 . The method of  claim 20  including selecting cylinder bushings as the component.