Anodizing is an electrochemical process in which a thicker oxide layer is created which not only protects the surface, but by adding certain colour shades can gain different colour tones.
In the process of anodizing, the aluminium is plunged into a vat with electrolyte where it is connected to the positive pole of the regular electrical source and through it becomes an anode. With the regular voltage the oxide anions travel from the cathode to the anode where they give off the oxygen. This reacts with the aluminium and produces aluminium oxide. The thickness of the oxide layer depends on temperature, electrolyte – H2SO4, voltage used and anodizing duration. Formed oxide layer consists of numerous open pores, which need to be closed. We can do that by sealing process. The anodised layer can be coloured in different ways.
Screen-printing can be carried out on non-handled and anodized aluminium surface. Permanent results can be achieved especially when printing is implemented while anodizing, and later closing of the micro-pores. Oxide layer pores absorb the colour and by closing the pores protection against wear out is increased.
Table: Recommended layer thickness at anodizing
|Layer thickness in µm||Field of usage;|
|25||External usage: surface is exposed to very strong influence because of corrosion or wearing out.|
|20||External usage: strong or normal influence, for instance building materials, vehicles and ships|
|15||External and internal usage: |
- relatively strong influence in the interior, for instance railing,
- external decoration details.
|10||External and internal usage: |
- regular interior and exterior influence in dry and clean environment.
Reflectors, borders, finishing car reels, sport requisites.
|5||Internal usage: regular influences.|