Electrocolouring (or electrolytic colouring) of aluminium is one of the most effective methods for colouring this material.

This is an electrochemical process in which an anodized component is immersed in an acidic solution containing metal salts and, where necessary, chemical additives.
Under these conditions, the component is subjected to an alternating electric current. As a result, metallic particles are deposited in the form of oxides within the porous structure of the anodized layer.
More specifically, tin salts are deposited in colloidal form inside the pores of the oxide layer created during the previous anodizing process.

In this way, a specific colour is produced depending on the metal salt used in the electrocolouring process.
The colouring oxide is deposited from the base of the pores upwards, typically reaching a depth of 2–10 mm within the anodized layer.

The resulting colour is highly resistant and durable over time.
A wide range of shades can be obtained, generally ranging from stainless-steel tones to black, including bronze, champagne and other intermediate colours. The final colour also varies depending on the immersion time in the colouring bath, as well as on the alloy used and its surface preparation, such as tumbling, polishing, degreasing, and other treatments.

The choice of alloy therefore influences the final result and should also be made according to the intended application of the material.
Different alloys have different characteristics, are better suited to specific colour finishes, and provide specific final performance properties.
To select the alloy best suited to a particular requirement, it is advisable to consult the relevant UNI tables for alloy classification.
After the preliminary treatments and finishing operations, followed by anodizing and colouring, the final step is sealing, which can be carried out either at low or high temperature.
Its purpose is to preserve the material’s corrosion resistance and aesthetic characteristics over time.

The purpose of aluminium electrocolouring is therefore varied. This process can meet a range of requirements, including:

• Decorative
  In this case, the aim is to meet specific aesthetic requirements through the colouring of the material.
• Functional
  In this case, the aim is to increase the level of protection provided to the aluminium.

When the metallic colloid is deposited at the bottom of the oxide pores, it creates a protective effect against atmospheric and chemical agents through the formation of aluminium oxide on the surface.
This improves resistance to corrosion, wear and abrasion, while also increasing the surface hardness of the material.
As a result, aluminium becomes suitable for use in outdoor, corrosive or otherwise more aggressive environments.

Given the advantages of the electrocolouring process, it is widely used across a broad range of industries.
The sectors that most frequently make use of this treatment include mechanical engineering, food and packaging, automotive, marine, technology, architecture, railway, lighting, foundry, window and door systems, furniture, and die casting.