A peeling metal garage door is one of the most common garage maintenance issues and, while it can look daunting, the process of repainting it successfully is achievable with the right preparation and materials. Thorough preparation is the key step that determines whether the new paint lasts years or months.

Why Peeling Happens

Paint peels from a metal garage door when moisture reaches the steel beneath the paint layer and causes rust to form. The expanding rust breaks the adhesion between paint and metal, causing the paint to lift and peel. The underlying cause is either the original paint coat was applied without adequate surface preparation, the door has been damaged, or the paint has simply reached the end of its service life after many years of weather exposure.

Step 1: Remove All Loose Paint

Use a paint scraper, wire brush, and coarse abrasive paper to remove all loose and peeling paint. Be thorough: any paint that is not well bonded to the steel will continue to peel once the new coat is applied over it. A wire cup wheel on an angle grinder is the most efficient tool for removing paint from large areas. Remove paint back to bare steel in all areas where adhesion is compromised.

Step 2: Treat and Prime Bare Metal

Any bare steel must be primed immediately after it is exposed to prevent new rust from forming. Apply a rust-inhibiting metal primer to all bare areas. For any existing rust, use a rust converter product that chemically converts iron oxide into a stable compound before priming. Allow the primer to dry fully according to the manufacturer's instructions before proceeding.

Step 3: Feather the Edges and Apply a Full Primer Coat

Sand the edges of the remaining sound paint to a feathered edge so they blend into the primed areas. Apply a full coat of metal primer to the entire door surface. This creates a uniform base for the topcoat and covers any step between the sound paint areas and the newly primed bare metal areas. Allow to dry fully.

Step 4: Apply the Topcoat

Apply two thin coats of weather-resistant enamel or exterior metal door paint, allowing full drying time between coats. A foam roller produces a smoother finish than a brush on flat panel areas. Brush the edges and any recessed sections. Two thin coats provide better adhesion and coverage than one thick coat.

Summary

Remove all loose paint back to bare metal. Apply rust converter to any rust, then prime all bare areas immediately. Feather the edges of sound paint and apply a full primer coat to the whole door. Apply two thin topcoats of weather-resistant enamel. Paint in dry conditions above 10 degrees Celsius. Thorough preparation determines whether the new paint lasts.