Unlike wood, metallic surfaces are slick and nonporous, making them unsuitable for paint adhesion. If you try to paint over metal bunk beds with ordinary bonding primer and paint, you will inevitably see flaking in a short amount of time. Fortunately, you can paint a metal bunk bed if you know the proper way to abrade the surface to promote adequate adhesion. You should also know the proper application techniques that can prevent brush strokes in the final finish.
Set up work space outdoors or in a ventilated area like an open garage.
Remove the mattress and all bedding.
Dampen a rag with mineral spirits, and wipe down the metal bunk bed. Allow 10 minutes for the mineral spirits to dry.
Cover parts of the metal bunk bed you don't want painted with painter's tape. Protect flooring with fabric drop cloths.
Apply a very thin coat of etching primer using a 2- to 4-inch latex paintbrush. Allow the primer to cure for four hours, effectively abrading the metal to ensure paint adhesion.
Wash the latex paintbrush using water.
Apply a very light coat of oil-based paint to the metal bunk bed using an oil-based paintbrush. Do not attempt to cover the surface in the first coat as this will lead to brush strokes in the final finish.
Allow the paint to dry for two hours and then apply another very light coat of paint. Allow the second coat to dry for two hours and apply additional coats until the etching primer is completely covered.
Clean the oil-based paintbrush with mineral spirits.