Priming steel beams - important information


If you want to give steel beams a new paint or a new protective layer, you first have to prime them. Which surface treatments are necessary before priming, what types of primers are there and what tasks they meet, you can read here.

Need for priming

For many types of paint, you must use a primer that is exactly matched to the topcoat used. However, if you use acrylic paint, an additional coat of primer is sufficient (often it can even be omitted).

With acrylic paint, it is sufficient if a bare metal surface is present. He is liable due to its physical peculiarity on metal surfaces without additional adhesion. You can work with acrylic paint in the so-called "one-pot system" - that is, you can use one and the same paint as a primer, intermediate coat and topcoat on a workpiece. This makes acrylic paint particularly economical. You can simply dilute it with water.

Galvanized steel beams

Before you can prime a galvanized steel beam, you must first perform a pretreatment. For the so-called zinc wash mix:

  • 1 liter of ammonia (25% from the pharmacy), often enough ½ liter
  • 10 liters of water
  • 10 ml of detergent

With this mixture, thoroughly rub the steel beam until the zinc wash agent is properly foamed. Then rinse with clear water. Then a primer can be applied, then the primer (or acrylic varnish).

Primer as rust protection

Steel girders that are not or only slightly protected against rust should always be provided with a rust protection primer. Such primers can have a different level of protection. In any case, make sure that the levels of zinc and phosphoric acid (the two main effective rust inhibitors in the primer) are as high as possible. Existing rust must first be completely removed (sanded down, sand blasted) and rust converter applied.

bonding agent

Whether a primer is required for metals depends on the particular primer used. Always pay attention to the specifications of the manufacturer and always use products from a series, as series are always perfectly matched to each other.

Primer and topcoat

Even primer and topcoat are always matched if they come from the same manufacturer and is part of a series. Again, using related products in a series is highly recommended.

Tips & Tricks

Before applying a primer, always ensure that the surface is clean, dry, rust-free, undamaged and absolutely free from grease (if necessary, degrease with a suitable agent). Otherwise, there may be problems with the adhesion of the primer.


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