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Knowledge Bank

WIOPEDIA - The WIOTEC® electroplating encyclopaedia

Knowledge from A - Z


Coloring of metals

Colored coatings on metallic objects are produced by various processes adapted to the metal in question.

Example copper:
A blue-black or brown coloration is produced by the formation of copper sulfide. With sodium hydroxide/potassium persulfate, copper becomes jet black. Cherry red copper is caused by potassium or sodium nitrite fusion and is called copper oxide. A greenish patina coloration is produced by copper nitrate solutions that are heated.

Various permanent tarnish colors can be obtained on steel by heating, and blackening turns steel black.

Silver treated with sulfur liver solution produces a brown old color.

Anodically produced oxide layers on aluminum have a porous structure and are therefore able to incorporate various organic or inorganic dyes (e.g. indigo dyes or various metal complexes). It is also possible to produce an inherent coloration in the "one-step anodizing process".

In "two-step color anodizing", colorless oxide layers produced by conventional anodic oxidation processes are colored in suitable metal salt solutions using single-phase alternating current. Tin, copper, nickel, silver and iron salts are used for this purpose; these are reduced to the free metal and incorporated into the pores of the oxide layer.

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WIOTEC® Ense GmbH & Co. KG
Auf den Geeren 9-11
59469 Ense-Höingen, Germany

WIOTEC® Arnsberg GmbH & Co. KG
Wagenbergstraße 55
59759 Arnsberg, Germany

+49 2938 97833-0
+49 2938 97833-20

From metal to precious metal
The company WIOTEC® is your specialist for surface finishing and metalworking. In our electroplating shop, which is managed according to the latest environmental standards, we are capable of finishing both small parts and long parts of up to six meters. This makes us one of the leading and most efficient decorative surface coaters in Europe.

Our most important resource is our employees - with their commitment, competence and experience. Together with them, we work out and develop individual and tailor-made solutions for our customers. From detailed consultation and planning to purchasing, mechanical and chemical pre-treatment, professional electroplating and supplementary services - WIOTEC®'s range of services leaves nothing to be desired.



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+49 2938 97833-11

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