Metal Fence Painting Tips
It's possible to make a metal fence look new again with paint, but be prepared for a lot of work.
Removing Any Rust
Old metal fences tend to have rust spots. The level of rust will depend on your climate and the age of the fence. When working on a metal fence, make sure the weather will be dry for several days (ideally at least a week) and moderately warm. Try not to work when the temperatures are too warm or if the humidity is high.
Begin by removing most of the rust using a sturdy metal wire brush. Do this during the coolest part of the day since this is extremely strenuous work and you don't want to overheat. The process is also hard on your hands. Unless your hands are very calloused, wear gardening gloves or work gloves to protect them. Scrubbing the fence with a wire brush will remove all the loose rust from the surface but will not get rid of the more established rust.
Put on rubber gloves; generously soak as many rags as you need with mineral spirits and scrub off as much of the remaining rust as possible. Replace rags as they become soiled and be prepared to throw them out since it'll be difficult to wash out the rust stains. If your fence was significantly rusted, don't be surprised if you're unable to remove every piece of rust.
Remove Dirt and Debris
You will be priming the fence, and you need to make sure the fence is clean in order to make sure the primer properly adheres. Wash the entire fence with hot water and soap. You may want to use a dishwashing brush to scrub away all traces of dirt and mineral spirits. Use a hose to rinse off the metal fence and allow it to dry overnight.
Apply the Primer
As with all painting jobs, it's important to apply primer to the freshly cleaned metal fence before applying the paint. Choose an oil-based primer that can be used on metal that also has a rust inhibitor. If you're working on a chain fence you may find the primer is too thick to apply without clumps. Thin the primer with mineral spirits a little at a time until you get the consistency you need. You probably won't need to thin the primer if working on a wrought metal fence.
Apply the primer with a narrow brush in even strokes. If working on a chain link fence, you may find that a larger artist's paintbrush will work better at applying even coats. Chain link fences tend to take longer to prime and paint because of the way they're made so take this into consideration when deciding how much time to set aside for this project. Make sure there are no streaks or bubbles in your primer application.
Painting the Metal Fence
Wait at least 24 hours for the primer to completely dry before applying the paint. Make sure you use an oil-based latex metal paint. Apply the paint in the same way as you applied the primer. Follow the manufacturer's instructions regarding drying time to make sure you don't end up with a streaked finish when you apply additional coats.