If you have a cast iron planter filled with ornamental plants, you have quite a dilemma. The very thing that your greenery needs to thrive is the biggest enemy of your planter: water. Water causes your cast iron planters to rust. Once the rust is established, you must remove it immediately to stop corrosion and preserve your planter. After planting a garden urn, the last thing you want is to uproot plants and dump out the soil to remove rust. Instead, the key to protecting an urn is to take preventative steps to protect it.
Inspect your planter for signs of rust. Eliminating rust before it can corrode a cast iron surface will keep your planter in good condition.
Remove rust spots by rubbing your planter vigorously with a wire brush.
Paint your cast iron planter to shield it from the elements. According to Barbara Israel, owner of Barbara Israel Garden Antiques, painting cast iron is how the Victorians protected their cast iron urns. Some Victorian iron garden pieces may have up to 21 coats of paint on them that have been added over time.
Allow the first coat of paint to dry. Then brush on a second coat of paint. Multiple coats of paint will give the planter the aged texture of old iron.
Rub paste wax over the surface of the cast iron to protect it from moisture.