Stain aluminum

The term "pickling aluminum" may be a bit confusing for do-it-yourselfers, as it is used differently when pickling wood. Nevertheless, the pickling of aluminum is an important process to replace the oxidation layer on the light metal. Afterwards you will learn how to pickle aluminum and which other work steps may still be necessary depending on further processing.

Metal oxidizes - also aluminum

Like any other metal, aluminum reacts chemically to certain influences and forms an oxidation layer. In addition, there are other circumstances that contribute to the fact that the aluminum can also be "dirty". So the following layers can be on aluminum:

  • dirt particles
  • layer of fat
  • oxide

Degrease aluminum

Dirt and grease layers can be removed by degreasing aluminum. But it is not always sufficient to degrease the aluminum exclusively. This is especially true when the oxide layer needs to be removed. Then, instead of degreasing the aluminum, you can strip the light metal immediately.

When pickling, the cleaning effect is more intense

Put simply, pickling does not differ greatly from degreasing aluminum. It is just more aggressive, so that the oxide layer can be replaced. This is important, for example, if you want to solder the aluminum. Because without the removal of the oxidation layer soldering does not work.

Typical products for pickling aluminum

For the pickling of aluminum different acids come into question, which are diluted in water. Typical acids used to pickle aluminum would be sulfuric acid or nitric acid.

The process of pickling first prepares the acidic solution diluted with water. Then immersion baths are carried out in the dilute acid with the relevant workpieces made of aluminum. Of sulfuric acid is often mixed with sodium dichromate.

Caustic soda for pickling with aluminum

Less dangerous and used again and again by craftsmen is pickling with a much less aggressive solution based on caustic soda. This technique of pickling aluminum is used especially when the aluminum is to be glued. In addition, the light metal must also be pickled when the aluminum is to be chrome plated.

Pickling is not only used for cleaning purposes

In addition, aluminum is not only pickled for cleaning purposes. It also represents a surface treatment in which different properties of the surface can be adjusted:

  • Matt surface
  • Shiny surface
  • Leveling the surface

Also burr and span can be removed too. Before aluminum is galvanized, it must also be pickled. With the help of hydrofluoric acid, which is largely banned in Germany, the silicate in the aluminum alloy is destroyed because it can not be electroplated.

Tips & Tricks

It may be that after the pickling again a conversion layer must be applied. In principle, this is again an oxidation layer, which can then be set concretely with different properties. For example, a very rough surface, so that paints remain more adherent when painting aluminum.

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