Before you attempt painting over the galvanised metal on your roof or wendy house, there are a few things that need to be considered first. When you want to paint galvanised metal, you need to ensure that the surface of the metal is completely free of any alkaline build-up. Oil- or alkyd-based paints are not recommended for use on galvanised steel. Instead, you should use a metal primer specifically designed for use on galvanised steel. This can then be followed with a coat of latex paint. Any newly galvanised surface is normally quite tricky to paint due to its smooth surface that doesn’t provide a good bond for the paint. The treatment used on galvanised metal in an effort to prevent rust also needs to be completely removed before any kind of painting can begin. To top all of this off, the zinc that is applied as a protective layer can also react with certain types of paint. This will result in a lack of adhesion and your paintwork will start to peel in no time at all.
So how do I get it right?
Achieving success when you paint galvanised metal relies heavily on proper preparation.
- If you are painting newly galvanised metal you need to clean the surface thoroughly with water so as to remove dust and dirt. You may then use a degreaser to further clean the surface. Once this preparation is complete, rinse everything thoroughly with clean water.
- If you are painting over galvanised metal that has been painted once before, you will need to use a suitable detergent in order to wash down and remove all traces of dirt. Allow the metal to dry. If the old paint is glossy you will need to sand the entire surface down and follow up with a damp cloth to remove all of the built-up dust. Remove iron rust with a wire brush or with a good sanding-down. It is best to prime bare steel the same day that it is cleaned. Lay drop sheets down to protect the area around the steel from the paint. Apply a primer designed specifically for galvanised surfaces. Always check the primer manufacturer’s recommendations as the process may differ between manufacturers.
Once your primer is dry, you can proceed to paint the surface with a paint recommended by an expert.