One of the challenges of painting a metal roof or building is how paint coatings will stay on the surface of the metal panels. While the metal building can be painted to beautify it, it can as well be painted to protect it from rust corrosion and deterioration. Using lighter or reflective colors are energy savers as well.
Just like when you are painting other structures, you want to ensure that the surface of the metal is clean. Pressure wash the surface on low flow and water to rid the metal panels of oil, dirt, rust, trapped moisture, mildew and peeling paint.
In addition, you may have to use a wire brush and sandpaper to scrape rust or loose paint before you power wash the panel with water. Also, it’s a good idea to add TSP to the water and spray the siding or panels. Add trisodium phosphate to your water and apply with a garden sprayer on a steel siding. Rinse clean and leave to dry for at least two days.
After the metal panels have dried, cover the doors, windows, and trim with painter’s tape or plastic sheeting to protect against overspray or drips.
Apply a rust inhibiting or galvanizing primer over the scratches and other dents or flaws on the metal panel. For aluminum, apply primer using a roller or paint sprayer and start from the top, moving across and work downwards. Bonding primers are best. Leave the panel to dry for 24 hours. Make certain to use the right primer that works well with a metal building especially if the old paint is coming off.
If your metal is laden with rust; whether surface or pitted, a rust converter is the way to go! The theory of a rust converter is to bring the rust back to metal. Over the years we have used OSPHO with success. Wire brush, scrape and sand troubled rust spots. Then apply the OSPHO product, wait 24 hours. The rust converter will turn blackish, then clean and apply an oil primer. Top coat as usual.
Use a paint sprayer to paint the metal building after the primer has dried. Use acrylic latex house paint to paint the metal building except the previous paint is oil-based paint, which requires oil-based primer and then latex paint. Allow the painted panels to dry thoroughly before applying the second coat. There are several color options for a metal building to accentuate the aesthetics of the building and protect from damages.