Anodizing: the oxidation process that protects metals
Anodizing, or anodic oxidation, is a non-spontaneous electrochemical process applicable only to aluminium in which a protective layer is formed on the surface of the aluminium, reinforcing its corrosion resistance.
Electro-oxidation is a protective treatment with applications in many areas, from the home to industry.
It involves a film with a thickness from 5 to 20 microns, so the size of the object is not affected.
Anodizing is performed only on aluminium, yielding a reaction between the metal and oxygen that promotes the formation of aluminium oxide. This settles on the surface of the object, creating a protective layer.
Anodizing treatment for aluminium alloys can create either the natural colour of aluminium or be coloured. The treatment is also requested for its aesthetic qualities, when visual appearance is a decisive factor that must be maintained over time.
How does the anodizing process work?
In industry, anodizing entails three stages:
- Preliminary treatment or chemical/mechanical pretreatment: several processes may be applied, whether chemical, mechanical or a combination of the two, involving mechanical brushing, degreasing, etching, neutralization and pickling;
- Electro-oxidation: after preliminary treatment comes the anodizing process itself, in which an oxide film is created on the metal, making it extremely porous. Such porosity creates the ideal conditions for colouring;
- Finishing: this phase involves three steps. The first is the colouring. Then comes sealing in demineralized water to close the pores and make the oxidation layer glassy and waterproof, creating a surface that is more resistant to corrosion. The last step is oiling, which serves to remove any residual dust from the sealing step.
The first phase therefore consists in the application of pre-anodizing treatments. Then, depending on the specific needs, degreasing or cleaning is done, along with etching or vibratory finishing. Processes can be applied individually or in combination.
The actual electrochemical process occurs in the second phase, in which the aluminium oxide film is formed, covering the surface of the metal.
The third phase, finishing, is used to treat the porous surface and make it waterproof. The subsequent oiling process removes the sealant dust.
Argos anodizing treatments
Anodizing is mainly applied to mechanical parts installed on machinery and in the automotive, aeronautics, chemical and oil & gas sectors, and all markets where a high resistance to corrosion and wear is required, along with a high quality appearance.
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