Metal stainings

1. Characteristics and properties

By aging the electroplated layers or the base material, optically very attractive results can be achieved. It is possible to “new” within a short time to optically age decades, to achieve outstanding spatial effects with cast or engraved workpieces and to give relief a more plastic effect.

Metoba offers old colours for copper with Bracol (brown-black) as well as with sulphur liver (grey-black). The use of the individual processes depends on the desired ageing effects and the preceding layer systems. For the generation of ageing effects on silver, we can offer a spectrum from brown ageing traces with sulphur liver to grey-black colouring. The layers produced on copper and its alloys as well as on silver are exclusively oxide layers, which would also automatically appear after a few years if the workpieces were to age accordingly, but not in this constellation of layer structure and uniformity with regard to layer thickness and colour shade. The average layer thickness of the produced dyes is 2µm. All the dyeings produced are classified as harmless to health and are both non-slip and relatively abrasion-resistant.

In order to achieve the actual ageing effect, it is necessary to mechanically process the workpieces after artificial ageing. For this purpose, the workpieces are partially brushed or wiped with pumice powder. It is also possible to achieve impressive optical effects on flat surfaces by scratching them later. In a relief image, for example, the recesses remain deep black, while the burrs and edges are mechanically reworked to reproduce the undercoat in its original colour. In order to preserve and protect the coatings produced in this way effectively and over a long period of time, and to keep them permanently non-slip, it is advisable to paint or wax them as the final finish.

2. Benefits and areas of application

The colouring of metals is used in many areas. For example, in the clothing industry for buttons for trousers, shirts and blousons, in the jewellery industry for chain pendants and rings, for art objects and the like.

Colourings can also be used to solve technical problems, e.g. glare-free surfaces for solar or camera parts.

3. Basic material

After material-specific pre-treatment, workpieces made of copper and copper alloys of any kind, zinc die-casting as well as steels and stainless steels of any kind can be refined by colouring metal surfaces. In our company it is possible to apply metal colourings on copper, brass and silver layers.

4. Required delivery condition

The goods provided must be largely metallically bright. Residual oils or residual impurities must be removable with conventional aqueous alkaline degreasers. Oils containing silicone, alkali/alkaline earth and high-pressure additives must be avoided at all costs.

5. Pre-treatment

Depending on the desired application it is absolutely necessary to coat the workpieces with a sufficiently thick coating of copper or silver in order to fulfil the requirements for colouring. In order to produce an optically high-quality surface, the workpiece must have a surface structure that is free of dirt, grease and oils.