Surface Treatment of Aluminium

From architecture to medicine devices, from machinery to sports equipment, from automotive to aircraft building: aluminium fulfils most the specifications needed. Your application determines the choice of surface treatment, whether as technical specification or as visual impression of the final product.

The processes are fixed and described as standards internationally. Although there are additional ambitious quality specifications in the field of anodising and powder coating created by quality label organisations.

Have a look at our certificates.

Standard Anodising

Anodising is an electro-chemical process, which transforms the aluminium’s surface into aluminium oxide. The oxide film is strongly connected with the basic material and its thickness can be suited appropriate to the work piece’s application.

The film is hard and porous what makes anodised aluminium wear and corrosion resistant. Anodised films can be coloured through infiltration of metal salts and organic pigments.

The anodised film is both environmentally protective and cleaning friendly. Last but not least it shows an appealing decorative look.

Hard Coating

Hard coated surfaces cover all electrolytic processes on aluminium that develop protection layers with high hardness coefficients. Hard coated aluminium parts serve as wear protection, but additionally enhance corrosion protection and show good tribological and lubricative characteristics.

Opposite to conventional anodising, which is processed at room temperature, hard coating processes are conducted at very low temperatures and at a considerable higher current density.

Hard coating is performed in sulphoric acid, but there are some processes using different acids or mixtures of acids, which may influence the surface characteristics.
Hard coatings show a completely homogenious hardness in every part of the surface, whether close to the basic material or near the outer surface.

Depending of the aluminium alloy used the resulting surface hardness is about 350 and 450 HV 0,025 (mikrohardness Vickers).
Hard anodised aluminium parts are used in technical applications, e.g. bolts and bearings. For the anodised film is a very bad conductor, treated aluminium is sometimes applicated in electrical isolations..

Coloured Anodising

Apart from natural anodising Eloxal Gerlingen offers the colouring of aluminium with lengths up to 8.000 mm. Depending on your requirements and applications you may have the choice between dye colouring and electrolytic colouring in a two step process.

Because the colouring process is influenced by a variety of factors limit samples (dark and light limits) have to be agreed on ahead of processing.


If you have additional questions, don’t hesitate to contact us.

Elektrolytic Colouring

One of the great advantages of anodised surfaces is the possibility to colour aluminium in a big variety. With electrolytic colouring metal salts are deposited in the pores of the surface under electric current, which are eventually sealed. The surfaces keeps it’s metallic visual impression, the s used are light fastened and therefore good for long-lasting applications.

We offer colourings in light to dark bronce and black (C 31 to C 35)

Organic Colouring

With organic colouring processes, the anodised surface is dyed in a solution consisting of organic colour pigments. For the variety of s used is huge, a broad range of different s can be performed.

Most well-known organic coloured applications are light gold (EV2) and gold (EV3). Both are light fastened.

Sandalor Colouring

Sandalor colouring is a combined process composed of electrolytic colouring and organic colouring. At a first step, the surface is coloured electrolytically to determine the colour light intensity, and after that coloured with organic pigments, which fix the final appearance.

Sandalor colouring offers a wide range of compositions between different colours and light intensities (Blue, Red, Orange, Yellow, Green etc.)


Many of our customers asked us about surfaces that combine the advantages of aluminium with the finish of stainless steel.

Through a combination of a superb grinding appearance with anodising and an additional, very light colouring we could find a new surface, which looks very similar to stainless steel without suffering from high stainless steel prices.


Powder Coating


Aluminium powder coating offers decorative surfaces with a nearly unlimited colour variety. For this reason focus of powder coated aluminium application is the architectural sector with an increasing amount and highest quality ambition. The high quality surfaces are produced through branding of powder paint at about 180° C which has been applicated by electrostatic facilities before branding. Our speciality: Powder Coating with Pre-Anodising, filiform corrosion resistant and with enlarged guarantee.

  • Grinding, Brushing and Polishing (E1 to E5)
  • Microlising
  • Sawing – Drilling – Burring
  • Sheets and sheet applications
  • Folio protection of sheets and profiles
  • Anti-noise coating

This post is also available in: German