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AssigneeHenkel Kommanditgesellschaft auf Aktien
InventorsUwe Karmaschek, Achim Roland, Hubert Vennschott, Harald Wennemann
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The invention concerns a method of pretreating aluminum or aluminum alloy surfaces before application of a permanent corrosion-protective conversion coating treatment, in particular before phosphating in acidic phosphating baths containing zinc, a chromating treatment, or a chromate free treatment. The method is characterized in that the surfaces are brought into contact with acidic aqueous treatment solutions containing complex fluorides of the elements boron, silicon, titanium, zirconium, or hafnium, alone or in mixtures with each other, at total concentrations between 100 and 4000 mg/L and at a pH between 0.3 and 3.5. Following the pretreatment, the aluminum or aluminum alloy parts may, after shaping if necessary, be joined by adhesive bonding and/or welding to each other or to parts made of steel, zinc plated and/or zinc alloy plated steel, and/or aluminum or aluminum alloy plated steel.
A process for treatment of surfaces of aluminum and its alloys, said process comprising steps of:
A process as claimed in 4, wherein the treatment solutions used in step (I) additionally contain sulfate ions in concentrations between 1 and 30 g/l.
Dependencies are inferred from the claim text.