Electrolyte for the production of black surface layers on light metals

US5035781A · kind A · utility

Assignee

• Jenoptik Jena GmbH · DE

Inventors

• Jurgen Schmidt · Los Alamos, US
• Thomas Furche · Jena, DE
• Roland Erdmann · Jena, DE
• Marion Reichert · Jena, DE
• Ullrich Bayer · Bad Doberan, DE
• Peter Kurze · Pulsnitz, DE
• Thomas Schwarz · Plaisir, FR
• Joachim Schreckenbach · Limbach-Oberfrohna, DE
• Hans-Jurgen Kletke · Luckau, DE
• Andreas Hoffmann · North Bend, US
• Martin Heppner · Jena, DE
• Anja Hasse · Berlin, DE
• Dorith Schmidt · Jena, DE
• Annette Klaus · Jena, DE

Key dates

• Filing date: May 24, 1990
• Grant date: Jul 30, 1991
• Expiry date: May 24, 2010

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/12812
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

The invention relates to a cyanide-free electrolyte being harmless to the environment and to health which makes feasible the production of black surface layers on light metals or on alloys of the latter, preferably titanium, remaining deeply-black and adhesive even after extreme changes in the ambient temperature and having nearly equal values of the optical absorptivity of radiation and of the thermal emission capability (the .alpha./.epsilon.-ratio is about 0.95) by means of the anodic oxidation by spark discharge (ANOF-method). These layers are absolutely X-amorphous and show, hence, an ideal optically isotropic behavior regarding the reflection of radiation. Due to their minimum evolution of gases they offer a high thermovacuum stability. The electrolyte consists of an ammoniacal solution of K.sub.2 H.sub.2 PO.sub.4 potssium dihydrogenphosphate and K.sub.2 CRO.sub.4 potassium chromate. The homogeneity of the optically black layers is ensured by not using fluoride ions and employing acetate ions. Such layers comprise titanium, chromium and copper following ratios of CR:Ti=1:(1.9 to 2.2) and CR:Cu=1:(0.8 to 1.3).