Step 1
Remove the garage door's power source prior to repair. Unplug the power cord for the door or switch off the garage's power at the building's circuit breaker.
Step 2
Apply dish detergent to the rusted panels. Scrub the rusted areas vigorously with a soft brush.
Step 3
Clean the detergent and rust from the door using a rag dampened with warm water. Examine the door for remaining rust damage.
Step 4
Sand any remaining rust with a coarse-grit sandpaper until all rust is removed. Start with a coarse-grit sandpaper, and then switch to a fine-grit sandpaper if a smoother finish is desired.
Step 5
Apply a rust-inhibiting primer to the repaired areas. Check that the primer is compatible with steel and rated for outdoor use. Zinc chromate-based primers are a common outdoor metal primer. Allow the primer to dry.
Step 6
Paint the repaired area to match the existing garage door color and gloss. Allow the paint to dry, then restore power to the garage door.