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

US12065754B2 · kind B2 · utility

Assignee

• thyssenkrupp Rasselstein GmbH · DE

Inventors

• Christoph Molls · Bonn, DE
• Birgit Bergholz · Mendig, DE
• Gerhard Menzel

Key dates

• Filing date: Oct 3, 2022
• Grant date: Aug 20, 2024
• Expiry date: Oct 3, 2042

Classification

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

Abstract

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.