Henkel Ag & Company, Kgaa

Roland Popp

Jan-Willem Brouwer

Frank-Oliver Pilarek

Matthias Hamacher

Marc Balzer

Jens Kroemer

Jens Krömer

A multistage method for treatment of composite metal structures containing metallic surfaces of aluminum, zinc and optionally iron, is provide wherein in a first step, selective zinc phosphating of zinc and ferrous surfaces proceeds using a phosphating solution containing a quantity of water-soluble inorganic silicon compounds sufficient to suppress white spot formation on zinc, but less than the quantity where zinc phosphating loses selectivity. In a following second step, aluminum surfaces are passivated with an acidic treatment solution. Also provided is a zinc phosphating solution suitable for said method containing at least 0.025 g/l, but less than 1 g/l of silicon as water-soluble inorganic compounds calculated as SiF, wherein the product (Si/mM)&#xb7;(F/mM) of the concentration of silicon [Si in mM] in the form of water-soluble inorganic compounds and the concentration of free fluoride [F in mM] divided by the free acid point number is no greater than 5.

Method for selectively phosphating a composite metal construction

A process for the anticorrosive treatment of metal components that have been heat-treated at a temperature of at least 100&#xb0; C. and at least partially comprise zinc surfaces, wherein the surfaces of the component that consist of zinc already partially have a crystalline zinc phosphate layer, wherein the cleaned component is given an activating pretreatment with an acidic aqueous dispersion of insoluble phosphates having a pH of not less than 4 and the component is subsequently subjected to a phosphating conversion treatment before electrocoating is applied. The invention also comprises the use of metal components that have been treated in such a process, for the application of multilayer systems and in particular for the manufacture of bodies in automobile production.

Optimized electrocoating of assembled and partly prephosphated components

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Manching, Germany

Roland Popp