Seal aluminum

The sealing of aluminum is an extensive topic. The sealants range from a non-transparent varnish layer over the natural to the artificial oxide layer and other techniques. What has to be considered when sealing aluminum, which processes exist and when they can be applied, we have summarized here for you.

Surface finishes decide on sealing techniques

Aluminum surfaces can be refined by numerous processes. Some of these methods already provide a seal, other surface finishes require additional sealing. But first some techniques for refining the aluminum surface:

  • Polishing and grinding aluminum (matt and high gloss)
  • Brush aluminum
  • Oxidize aluminum (natural and artificial)
  • Paint aluminum
  • Surface compacting with glass bead blasting
  • chrome plating, nickel plating, coppering aluminum

The oxidation of aluminum surfaces

Aluminum forms an oxidation layer in air by contact with oxygen. This makes aluminum look dull and tarnished. For purely functional requirements, this natural "sealing" by oxidation may well be desirable.

Paints as aluminum seal

More and more car bodies are made of aluminum. So that no oxidation layer disturbs here, the aluminum is pickled. Afterwards, the aluminum can be painted, as the paint now adheres.

Therefore, when working on painted aluminum sheets, it is so important that old paints are never sanded to bare aluminum before the new finish, but only to the primer coat. The paintwork therefore not only has the task of a decorative painting, but is also a protective seal.

Polished aluminum seal and chrome plating as a seal

But now there are situations in which a special surface refinement is made. The high gloss polishing of aluminum is such a technique. Afterwards the surface is completely unprotected.

This is doubly annoying, because the high-gloss polishing creates a surface with almost the same reflection effect as when chrome-plating aluminum. This also includes copper plating, nickel plating, galvanizing, etc.

Chrome plating is not always a solution either

Aluminum rims, in particular, are often polished to a high gloss, as chrome plating is not permitted in Germany (chrome plating changes the microstructure of the aluminum and could make an aluminum rim more fragile). However, such a surface is extremely susceptible to alkalis, acids and, of course, scratches.

Clearcoats, silicone wax spray, special aluminum seals

Clear lacquer is only partially a solution for sealing, as this is yellowed and also dull. Other aluminum sealants, such as silicone wax spray, are great for protecting polished aluminum parts such as engine cowlings, etc., but are unsuitable for rims.

Especially where there is great heat, this sealing technique is not very efficient. Instead, you can use protective oils here, but they are relatively easy to remove mechanically and must be renewed frequently.

Instead, seal regularly and polish

Therefore, rims should either be high pressure compacted by means of glass bead blasting (there is also a high gloss), the surface is reasonably protected. But as with conventional polishing, you will have to perform this polishing again and again at regular intervals. For winter use such rims are completely unsuitable.

Anodizing (artificial oxidation) as an aluminum seal

Another way to densify such surfaces of aluminum is the artificial production of an oxide layer. This process is also known as "anodizing". You can anodize aluminum parts transparent and colored (the color pigments are stored after the actual and transparent anodizing in the oxide layer).

Tips & Tricks

The sealing can be very easy to very difficult to almost impossible depending on individual requirements. Especially with aluminum rims, you have to resort to products that are specifically compatible with the aluminum. There are also a number of seals that you can use here.

Clearcoats on aluminum rims have the disadvantage that water and oxygen can get in contact with the aluminum even through the slightest damage to the paint layer and then oxidize. With salt from the shining comes then still another corrosion. In addition, these must then be completely removed for cleaning the rims and then old paints, which means additional effort.

Video Board: How to Clean Off and Seal Aluminum Housings from Engine Coolant Corrosion