How to properly anodize aluminum

Mass production of aluminum structures and parts is associated with the unique properties of this material. It has a minimum specific gravity, is resistant to many aggressive media and can be easily processed. But for long operation of products it is necessary to anodize aluminum.

Why is it necessary?

During the interaction of any metal with oxygen contained in the atmosphere, oxidation of the upper layer occurs on the surface. This is called the formation of an oxide film, which prevents the spread of rust in the interior of the metal.

Depending on the type of material, the process of oxidation of the surface passes in different ways. Iron and steel practically do not form an oxide film, but precious metals (gold, silver, platinum) are protected from corrosion. Aluminum occupies an average position, so it requires the artificial creation of a film. This is especially important if a similar profile is used in the manufacture of windows. Anodized aluminum is resistant to external weather factors, which can lead to corrosion and a rapid loss of operational properties of the structure.

Technology

In order to form an effective protective film on the surface of the profile , it is required to anodize aluminum. The essence of the process is the transfer of molecules of another material, which is more resistant to oxygen, into the structure of the product. In addition, it is possible to artificially increase the oxide layer without the addition of other metals.

Regardless of the chosen method, it is necessary to fulfill the conditions for carrying out the technological process. It consists of the following stages:

1. Preparatory.
2. Anodizing process.
3. Fixing the interlayer.

For each of them, appropriate equipment and consumables are selected. As a result, a qualitative anodized aluminum should be obtained. This will make it possible to use the profile for the manufacture of facade and window structures.

Preparatory stage

The surface of the product is thoroughly cleaned from dust, dirt and debris. If there are irregularities or mechanical damages, they are eliminated even before anodizing. Next, remove the old oxide layer, otherwise it will prevent the even formation of the protective film.

After carrying out mechanical processing (grinding and degreasing), the profile should be placed in an alkaline solution. To properly anodize aluminum, you must first "etch" its surface. The formation of microcavities and unevenness increases the total area of the protective layer. Further, in the acid solution, the product is clarified. After completion of all stages, the aluminum must be thoroughly rinsed.

Anodizing

After passing the preparatory stage, it is possible to start the anodizing process. For this, the aluminum product is immersed in a special bath. The procedure is carried out with the help of crane equipment (for large structures) or by hand on ropes.

On the design of the bath must be said separately. It is a large container made of thick-walled stainless steel, into which 2 cathodes are placed. The immersion technology of the profile should be such that the electrolyte in the bath is in contact with the entire area of the product. As such a liquid, sulfuric acid is used, which makes special demands on the safety of production. If the product has a complex configuration, then it is better to use oxalic acid.

After immersing the profile by electrolysis, a protective layer begins to form. Its thickness directly depends on the composition of the electrolyte, temperature and current density. The higher the last value, the more oxide film is formed on the surface. After the completion of the procedure, the thickness of the layer can vary from 2 to 7 microns, depending on the technological parameters of the process.

Fastening

However, it is too early to stop anodizing aluminum - it is necessary to fix the formed surface layer. It will be a porous structure that will quickly peel off without treatment. In addition, it does not have the proper characteristics of hardness.

The fastening can be carried out by placing the product in fresh water, brought to the boiling point. According to another technology, the surface is exposed to hot steam. In either case, the oxide film is discarded and its molecular bond with the aluminum surface.

If in the future the profile is painted, then the fixing can be omitted. If the powder coating technology is observed, the film will be protected by heat treatment.

We found out what anodized aluminum is. This treatment of metal - a guarantee against the appearance of rust on the surface of the product. Anodizing technology is constantly being improved, and today it is possible to paint aluminum products with a cathodic reaction.