Jenoptik Jena G.m.b.h.

Technische Universitaet Karl-marx-stadt

Thomas Schwarz

Peter Kurze

Thomas Furche

Joachim Schreckenbach

Ullrich Bayer

Marion Reichert

Annette Klaus

Dorith Schmidt

Anja Hasse

Martin Heppner

Juergen Schmidt

Roland Erdmann

Waldemar Krysmann

Kerstin Haupt

Klaus Rabending

Andreas Hofmann

Hans-Jurgen Kletke

Karl-Heinz Hartmann

Bayer Ullrich

Maria Berger

Jurgen Schmidt

Hans-Juergen Kletke

Andreas Hoffmann

By means of an electrolyte free of ammonia, cyanide, and fluoride, hence low in harmful substances and inoffensive to the environment, optically black coatings having a thickness of less than 10 microns and substantially equal optical absorption and thermal emission capability can be produced on light metals or alloys thereof by spark discharge anodizing. In comparison with prior art conversion coatings obtained by spark discharge anodizing, the coatings produced with this electrolyte have a substantially lower roughness of this electrolyte in spark discharge anodizing provides an alternative mode of coating particularly for structural components or subassemblies of complicated shapes having greater requirements for accuracy to gauge.

Electrolyte for producing conversion coatings

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 (ANDF-method). These layers are absolutely X-amorphous and show, hence, an ideal optically isotropic behavior regarding the reflection of radiation. Due to their minmum 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 potassium 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 in ratios of Cr:Ti=1: (1.9 to 2.2) and Cr:Cu=1:(0.8 to 1.3).

Black surface layer on light metal

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).

Electrolyte for the production of black surface layers on light metals

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.

Method for the preparation of decorative coating on metals

Growing community of inventors

Karl-Marx-Stadt, Germany

Thomas Schwarz