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

US11396713B2 · kind B2 · utility

Assignees

• thyssenkrupp Rasselstein GmbH · DE
• thyssenkrupp AG · DE

Inventors

• Andrea Marmann · Piesport, DE
• Christoph Molls · Bonn, DE

Key dates

• Filing date: Dec 12, 2019
• Grant date: Jul 26, 2022
• Expiry date: Dec 12, 2039

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C25D17/02
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

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/dm2.