How is zinc normally used in paints?

Painting a galvanized door and how to do it

Zinc as protection against corrosion and the painting over of galvanized surfaces

Usually a galvanized surface is adequately protected from external influences and should prevent the metal from rusting. However, it happens again and again that galvanized sheet metal, which has been exposed to the weather for a long time, no longer looks particularly good and can also start to rust. If you want to paint such a surface, for example a galvanized door, there can be difficulties. The paint does not adhere easily to galvanized surfaces and can peel off after a short time if you do not sufficiently pretreat the surface.

Painting a galvanized door in several steps

Before the surface can even be painted, you should treat it sufficiently in order to create the load-bearing capacity for the paint. Only then does the actual painting take place. So, essentially, you need to do the following:

  • Thoroughly remove loose dirt and rust
  • Sand the galvanized surface thoroughly
  • clean the surface with zinc cleaner
  • apply a primer and allow it to dry completely
  • then sand the surface a little if necessary
  • apply the paint, preferably in at least two layers

The so-called wetting agent wash before painting

Before painting can be carried out, a so-called wetting agent wash must be carried out as part of a thorough cleaning. This serves to remove the zinc salts and to allow the primer and paint applied later to adhere. For this purpose, a mixture of pure ammonia and water is used, to which a little washing-up liquid is added. You have to apply this mixture and let it work for at least ten minutes. Then the surface is rinsed with clear water and must dry thoroughly.

It is best to use a suitable primer

Be sure to use a primer that is suitable for this purpose and apply it over the entire surface of the door so that the paint that is applied later holds well. Don't forget to let the primer dry a sufficient time before applying the paint.

Mark Heise
Article image: ton.minimalist / Shutterstock
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