How to properly anodize aluminum

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Mass production of aluminum structures and parts is due to the unique properties of this material. It has a minimum specific gravity, is resistant to many aggressive environments and is easy to process. But for long-term operation of products, it is necessary to anodize aluminum.

Why is this necessary

During the interaction of any metal with oxygen contained in the atmosphere, the top layer is oxidized on the surface. This is called the formation of an oxide film, which prevents rust from spreading deep into the metal.

Depending on the type of material, the surface oxidation process takes place 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 a middle position, therefore, it needs an 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 rapid loss of performance.construction properties.

Technology

In order for an effective protective film to form 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 adding 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 steps:

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

For each of them, appropriate equipment and consumables are selected. The result should be high-quality anodized aluminum. 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 of dust, dirt and debris. If there are irregularities or mechanical damage, then they are eliminated even before anodizing. Next, remove the old oxide layer, otherwise it will prevent the uniform formation of the protective film.

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

Anodizing

After passing the preparatory stage, you can start the anodizing process. To do this, the aluminum product is immersed in a special bath. The procedure is performed using crane equipment (for large structures) or manually using cables.

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

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

Securing

However, it is still too early to stop anodizing aluminum - it is necessary to fix the resulting surface layer. It will attach a porous structure, which, without processing, quicklypeel off. In addition, it does not have the proper hardness characteristics.

Fixing can be done by placing the product in fresh water brought to a boil. According to another technology, the surface is treated with hot steam. In any case, the oxide film is cured and molecularly bonded to the aluminum surface.

If the profile is painted in the future, then fixing can be omitted. Subject to the powder color application technology, the film will be protected as a result of heat treatment.

We found out what anodized aluminum is. Such metal processing is a guarantee against the appearance of rust on the surface of the product. Anodizing technology is constantly improving, and today it is possible to paint aluminum products using a cathodic reaction.