How to Paint a Metal or Steel Exterior Door

Rust spots bleeding through a white steel door. Paint lifting in sheets around the lock. A door that was closed too soon and now carries the weatherstripping’s print down one edge. Those are metal door problems, and each one comes from the same place: paint was put on a surface that wasn’t ready for it.

The short answer: treat the rust, degrease the surface, prime what needs priming, and use a paint made for exterior metal, applied in thin coats. For metal doors, Sherwin-Williams says removing any loose rust with a wire brush or other scraper is crucial, and that rusted areas should be spot primed with a rust-inhibitive primer.

What makes metal different from wood

Wood absorbs. Metal doesn’t, and that changes everything about how paint behaves on it:

• Nothing soaks in. The paint holds on because the surface is clean and lightly scuffed, nothing more, which is why degreasing matters more here than on wood.
• Rust spreads under paint. A wooden door with a bad patch stays a bad patch. Rust left under a fresh coat keeps going and pushes the paint off from beneath.
• It moves with heat. A dark steel door in afternoon sun expands more than a wooden one, so the paint has to stay flexible.
• Most “metal” doors are steel skins over a foam core. They dent rather than rot, and a dent that traps water is where the rust starts.

If the door is wood rather than metal, a wooden front door is a different job, with sanding and grain direction doing the work that rust treatment does here.

Rust is the job

On a metal door, rust treatment is the difference between a repaint that lasts and one that bubbles by spring.

1. Find all of it. Check the bottom edge, the part that gets kicked and scuffed, around the lock and hinges, and any dent or scratch. Rust starts where the coating was broken.
2. Expect the bottom edge to be worst. Through a New England winter, snow banks against a door for weeks at a time and salt gets tracked onto the sill, so the bottom inch or two takes harder wear than anywhere else on the door.
3. Take off everything loose. A wire brush, abrasive pad or scraper, back to sound metal. It’s the step people rush, and the one the finish depends on.
4. Spot prime immediately with a rust-inhibitive primer, before the bare metal has time to start rusting again.

Railings, frames and storm doors fail the same way, which is the subject of painting metal surfaces generally.

What paint to use on a metal door

An exterior acrylic enamel suits most metal doors. Oil-based and alkyd enamels still have a place, mostly where you want the smoothest possible finish and can give the door the time it needs. The two trade off like this:

• Oil-based and alkyd enamels. They level out beautifully, which is why old steel doors finished in them look almost sprayed. They’re harder, they take longer to dry, and they get more brittle with age, so they can crack where the door flexes.
• Exterior acrylic enamels. They stay flexible as the door expands and contracts, hold color in sun, clean up with water and recoat sooner. That flexibility is why they suit a south-facing door, or any dark color that gets hot.

Whichever you pick, it needs to be an exterior product, and the label needs to say it suits metal. The can tells you which primer it wants underneath, and that pairing matters more than which brand you buy.

When this door actually needs primer

You don’t always need to prime the whole door. Sherwin-Williams’ garage door guide, the closest thing it publishes to metal door advice, says primer is worth using if you’re covering a dark color with a lighter shade or want the new paint to grip better, and that it may not be necessary on a door that was previously painted and is still in good condition.

Always prime: bare metal, every rust spot, and any area sanded back. Usually prime: a glossy old enamel the new paint can’t grip, and any big color change. Rarely needed: a sound, matte, well-cleaned existing coat in the same color family.

Painting the door, step by step

1. Take the door down if you can. Tap a screwdriver up under each hinge pin to drive it out, starting at the bottom, and have someone steady the door as the last pin comes free.
2. Remove the hardware, or mask it carefully. Handles, lock plates, knockers, house numbers, and the weatherstripping if it pulls off.
3. Wash the door. Sherwin-Williams suggests a mild detergent. On an entry door that’s been handled daily, a degreasing cleaner is better around the handle and lock.
4. De-rust and sand. Loose rust off, glossy areas dulled, dust wiped away.
5. Spot prime rust, bare metal and repairs.
6. Two thin coats. Panels and recesses first, then the flat areas, keeping a wet edge. Thin coats are what stop runs on a surface that can’t absorb anything.
7. Don’t forget the edges, especially the bottom one, where water collects and rust usually starts.

Laying the door flat gives a better finish than painting it hung, for the same reason it does on wood: paint levels instead of running.

Older doors and lead paint

If the house was built before 1978, the older layers may contain lead, and scraping or sanding is what makes that a hazard. The EPA’s Renovation, Repair and Painting rule covers homes, childcare facilities and preschools built before 1978, and requires anyone paid to disturb paint in them to be certified in lead-safe work practices. Homeowners working on their own pre-1978 home are generally outside the rule, and the EPA still advises using lead-safe practices, because the dust is the risk either way.

In practice that means testing if you’re unsure, containing the debris, wet methods rather than dry sanding, and cleaning up properly afterwards.

What usually goes wrong

• Skipping the degrease. Hand grease around the handle is invisible and paint won’t hold on it.
• One heavy coat instead of two thin ones. Runs down the flat areas, and paint that stays soft underneath for weeks.
• Closing the door too soon. This is the one that ruins an otherwise good job, because each coat needs its full drying time before the door touches the weatherstripping.
• Painting in full sun. A dark metal door in direct sun gets hot enough to dry the surface before the paint has leveled out.

If you’re having it done, the questions worth asking are what the painter plans to do about the rust, and whether the bare spots get primed before any topcoat. A steel door that’s been prepped properly can look new for years, and one that hasn’t will tell you within months. If yours is rusting along the bottom or peeling around the lock, it’s worth looking at before the next repaint rather than painting over it again. If you’d rather not judge it yourself, we can take a look at the door before any exterior painting starts.