The Best Way to Paint a Steel House Door
- New steel house doors are made of steel sheet metal wrapped around an insulating foam core for energy efficiency. They will come preprimed from the factory and need no further preparation besides a light sanding with fine sandpaper or a sanding sponge and a wipe-down before painting.
Older, previously painted steel doors can be sanded and cleaned and need no further prep work before painting if they're in good shape. If the paint has worn down to bare metal you will probably find some rust, which must be treated. The easiest way is to use a spray can of metal primer. If the rust is starting to erode the metal, buy some rust reformer. This stabilizes the rust, turning it into a solid surface that will not rust further and can be painted over. Use a wire brush or scraper to remove all loose rust, apply the rust reformer and wait 24 hours before painting.
The door may have vinyl-framed window insets in it. These usually have a rubbery weather-proofing sealant around them with excess squeezed out around the frame edges. Use a sharp utility knife to cut away the excess. It might be slightly rubbery or sticky, but can be painted without priming. - Older steel doors may have dents and deep scratches. When the door is repainted these will become even more visible. Use Bondo or a similar filler used for repairing dents in automobiles for filling these. It is simple to use but fairly hard when dry, so an electric palm sander will make sanding them smooth much faster. Use metal primer on every patch.
Avoid the temptation to use regular spackle or wood filler. It's not designed to adhere to metal or other hard, smooth surfaces and will crack and eventually fall out. - Steel house doors can be painted with either alkyd (oil-based) or latex (water-based) paint. Latex paints are easier and faster to use, and if you use a high quality paint, will be as durable and good-looking as alkyd.
Consider the exterior color. Metal gets hot in direct sun, and using a dark color will both diminish the energy-efficiency of the door and cause the paint to fade and peel sooner than you might like. Unless the door is sheltered by a porch, choose a medium or light color. - Unless you want to go to the bother of getting a sprayer and masking off the entire area, the easiest way to get a nice paint finish on a steel door is with a brush and roller. Remove the hardware and weather stripping if you can, or use painters' blue tape to protect it unless you have a very steady hand. Use a small 3- to 6-inch foam or mohair mini-roller for the best finish. Do all the brush work first and roll last. Several thin coats of paint will result in a more even, smooth paint job than one or two thick coats.