Thyssenkrupp Rasselstein Gmbh

Thyssen Krupp Ag

Christoph Molls

Andrea Marmann

Thomas Lenz

Sebastian Hartung

Gerhard Menzel

Birgit Bergholz

Rainer Görtz

Andrea Dr Marmann

Rainer Gortz

In a method for passivating the surface of a tinplate using electrolytic deposition of a passivation layer containing chromium oxide/chromium hydroxide on the surface, the electrolytic deposition of the passivation layer is carried out at least partly from an electrolyte solution which contains a trivalent chromium compound, at least one salt for increasing the conductivity and at least one acid or one base for adjusting a desired pH value and is free from organic complexing agents and free from buffering agents. In order to increase the amount of chromium oxide in the passivation layer, after the electrolytic deposition of the passivation layer, the passivated tinplate is subjected to a thermal treatment in which the passivated tinplate is kept at a treatment temperature of 100° C. or more for a treatment time of at least 0.5 seconds.

Method for passivating the surface of a tinplate and electrolysis system for carrying out the method

A method of producing a metal strip coated with a coating, said coating containing chromium metal and chromium oxide and being electrolytically deposited from an electrolyte solution that contains a trivalent chromium compound and at least one salt for increasing conductivity and at least one acid or one base for setting a desired pH value, onto the metal strip by bringing the metal strip into electrolytically effective contact with the electrolyte solution during an electrolysis time. The metal strip is successively passed at a predefined strip travel speed in a strip travel direction through a plurality of electrolysis tanks successively arranged in the strip travel direction. At least the first electrolysis tank, as viewed in the strip travel direction, or a front group of electrolysis tanks is filled with a first electrolyte solution and the last electrolysis tank, as viewed in the strip travel direction, or a rear group of electrolysis tanks is filled with a second electrolyte solution. The second electrolyte solution contains no additional components apart from the trivalent chromium compound as well as the at least one salt and the at least one acid or base and is especially free of organic complexing agents and free of buffering agents.

Method of producing a metal strip coated with a coating of chromium and chromium oxide using an electrolyte solution with a trivalent chromium compound and electrolysis system for implementing the method

A method for the production of a metal strip coated with a coating. The coating containing chromium metal and chromium oxide and is electrolytically deposited from an electrolyte solution that contains a trivalent chromium compound onto the metal strip by bringing the metal strip, which is connected as the cathode, into contact with the electrolyte solution. An effective deposition of the coating with a high chromium oxide portion is achieved by successively passing the metal strip at a predefined strip travel speed through a plurality of electrolysis tanks arranged successively in a strip travel direction. The first electrolysis tank is set to a low current density; a second electrolysis tank, which follows in the strip travel direction, is set to a medium current density; and a last electrolysis tank is set to a high current density, where the low current density is greater than 20 A/dm.

Method for the production of a metal strip coated with a coating of chromium and chromium oxide using an electrolyte solution with a trivalent chromium compound

A method for producing a metal strip coated with a coating that contains chromium metal and chromium oxide and is electrolytically deposited from an electrolyte solution that contains a trivalent chromium compound onto the metal strip by bringing the metal strip, which is connected as the cathode, into contact with the electrolyte solution. An efficient deposition of coating with a high proportion of chromium oxide is obtained by successively passing the metal strip through a plurality of electrolysis tanks. The electrolyte solution in at least the last electrolysis tank, as viewed in the strip travel direction, or in a rear group of electrolysis tanks has an average temperature of at most 40&#xb0; C., and the electrolysis time, during which the metal strip is in electrolytically effective contact with the electrolyte solution in the last electrolysis tank or in the rear group of electrolysis tanks is less than 2.0 seconds.

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Bonn, Germany

Christoph Molls