Method for the preparation of decorative coating on metals

US4869789A · kind A · utility

Assignee

• Technische Universitaet Karl-Marx-Stadt · DE

Inventors

• Peter Kurze · Pulsnitz, DE
• Waldemar Krysmann · Plaisir, FR
• Maria Berger · Plaisir, FR
• Klaus Rabending · Gujungu, NG
• Joachim Schreckenbach · Limbach-Oberfrohna, DE
• Thomas Schwarz · Plaisir, FR
• Karl-Heinz Hartmann

Key dates

• Filing date: Feb 2, 1988
• Grant date: Sep 26, 1989
• Expiry date: Feb 2, 2008

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C25D11/026
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

The process for producing decorative coatings on metals is primarily used in the jewelry industry, in handicrafts, and in device construction according to the invention, matte, true-to-form decorative coatings with a homogenous thickness of 3 .mu.m to 30 .mu.m are provided means of an electrochemical and plasmachemical reaction using a pulse operation in aqueous electrolytes at voltage peaks of 250 V to 750 V, pulse times of 20 .mu.s to 2 ms, pulse frequencies of 35 Hz to 300 Hz, pulse currents from 20 A to 120 A, electrolyte temperatures between 318 K and 360 K, and average current densities from 0.1 A cm.sup.-2 to 1 A cm.sup.-2.