Jenoptik Jena G.m.b.h.

Jenoptik Gmbh

Ullrich Bayer

Thomas Furche

Thomas Schwarz

Kerstin Haupt

Peter Kurze

Joachim Schreckenbach

Juergen Schmidt

Anja Hasse

Marion Reichert

Annette Klaus

Martin Heppner

Dorith Schmidt

Roland Erdmann

Jurgen Schmidt

Andreas Hoffmann

Hans-Jurgen Kletke

A process for the production of white and black oxide ceramic surface films on silicon-containing light metal cast alloys by plasma-chemical anodic oxidation. An aluminum cast alloy is pickled with nitric acid and hydrofluoric acid and coated by plasma-chemical anodic oxidation in an aqueous electrolyte. Accordingly, a coating variant is provided particularly for construction parts of silicon-containing light metal cast alloys having complicated shapes which enables the production of uniformly thin oxide ceramic surface films in contrast to conventional coating variants.

Process for the production of oxide ceramic surface films on

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 (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

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Jena, Germany

Ullrich Bayer