The best way to repaint a metal building is to think like a Boy Scout. The motto for this organization has always been “Be Prepared.”
This is excellent advice for any painting project whether it’s a new surface or an older metal building that needs some attention. Not only should you make sure that you have the supplies and equipment you need before you start but you should focus on the word “prepare” before applying paint.
Your goal is to improve the appearance of the building, of course. But you are also going to improve the chances for this building to serve you for many more years. To accomplish both of these, you’ll need to get the metal surface ready to accept paint. If you’ve noticed signs of flaking or peeling paint or areas where the metal is beginning to rust, it’s time to paint. Other signs would be fading of color and a “chalky” appearance.
Dealing with Rust
When you’re repainting metal, it’s important to deal with even the smaller areas of rust and corrosion. Cracks and holes should be filled with a product that would be used to repair an auto body. Taking care of rust and corrosion may involve sanding and/or the use of a wire brush. Sandpaper in the range of 80 grit should be right for rust removal. Use a finer sandpaper such as 120 grit to smooth the surface as a second step.
If you have large, difficult areas of corrosion/rust, you could use the sandblasting technique. There are chemical products called rust converters that can remove the rust by dissolving it. These products generally provide a protective film on the metal surface as well. Be careful not to leave streaks where you expect a completely smooth surface.
Cleaning the surface thoroughly is essential. You may want to do some power-washing before you start the above repairs. It wouldn’t be a bad idea to do it again after you make repairs, though you’ll have to be careful not to cause further damage to the repaired areas. A more tender rise would be advisable. If it seems as though you’ve spent most of your time preparing the metal surface, that’s as it should be. Painting is the easy part.
Cover Doors and Windows
Now that it’s time to paint, you should take some time to cover the windows and doors that won’t be painted. Taping plastic over these areas should be sufficient. For larger buildings, you will probably be using a paint sprayer. Apply a good primer made specifically for these metal surfaces. You should work from the top of the side wall down and move slowly from one end to the other.
Make sure that your first coat is totally dry before applying a finish coat. Clean the sprayer completely, following the directions carefully, and then start painting in the same way with the finish coats. Your best option is an acrylic-latex paint designed specifically for metal buildings. Your paint supply or building manufacturer will also have some important guidelines for paint choice. Two coats are recommended for best results.
