If you are planning to paint galvanised corrugated roof panels, consider a pair of important points before you begin the application process. Galvanised panels are coated with zinc. This coating protects them from rust. Unfortunately, it also makes them ill-suited for paint adhesion. You must condition the roof panels to accept paint by applying a special acidic primer, capable of etching galvanised metal. You should also select a particular paint, formulated to expand and contract as temperatures fluctuate, or the finish may ultimately fail.
Use a ladder to access the corrugated roof panels.
Wash the corrugated roof panels, using a pressure washer equipped with a low-pressure tip. Wait approximately 2 to 3 hours for the panels to dry.
Protect areas beneath the roof panels with dust sheets.
Coat the clean corrugated roof panels with galvanised metal etching primer using a roller stocked with a nap cover. Use a 3- to 4-inch paintbrush to smooth the primer within the inundated areas of the corrugated panels. Wait 4 hours for the etching primer to dry.
Wash each of your painting tools with tap water.
Coat the primed corrugated roof panels with acrylic latex paint using the roller stocked with a new, fresh nap cover. Use the clean paintbrush to smooth the paint within the inundated areas. Use a roller extension pole if needed. Wait 4 hours for the paint to dry.
Add a second coat of paint if the primer bleeds through.
Never paint unprimed corrugated roof panels or the paint will peel. Don't use plain acrylic, latex or oil primer on a corrugated roof panels or the finish will eventually flake. Read the safety guide on the side of the ladder before you begin work.