Like any metal object that is kept outdoors, a metal garden windmill will need to be re-painted occasionally to prevent rust. Fortunately, you can finish this project yourself in a weekend, even if you have never painted metal before. Although a garden windmill can be painted in any color you choose, there are a few design tips you may want to keep in mind before getting started.
Color Selection and Design
Traditional windmills, long associated with the Dutch countryside, are generally not very colorful. The dominant colors tend to be brown and white. However, there are a few design ideas that you can borrow from this traditional aesthetic, even if you prefer a bit more color. Select two different colors for the body and the roof of the windmill. Traditionally, windmill roofs were constructed of a natural roofing material (usually thatching or slate), so they had a color that was distinct from the main windmill body color. Select a third color for the windmill blades. A three-color scheme is generally considered to be effective for decorative objects. More colors may get lost, and fewer colors may tend to flatten out the object, making it appear insubstantial. If you are following a traditional color scheme for the windmill—for example, a white body with a brown roof—the blades can be a great place to enliven your design with a bit of color. Bright red or yellow blades will evoke that other familiar symbol of Holland—the tulip—and will create particular visual interest if your windmill blades turn in the breeze.
When painting any metal object that will be exposed to the elements, proper preparation is the key to a long-lasting paint job. Dirt, rust, loose flakes of old paint, and other contaminants will interfere with the ability of the fresh paint to bond with the surface, necessitating re-painting much sooner than would otherwise be required. Scrape your metal garden windmill carefully with a five-in-one scraping tool, removing all loose patches of paint. Use a stiff wire brush to remove any rust spots or stubborn paint areas. If there are some patches of old paint that will not come off, scuff up these areas with a medium-grit sandpaper. This will help the primer to adhere to these areas. Finally, wash the entire windmill with a strong dishwashing detergent and water, repeating until the water rinses clear. Allow the windmill to dry thoroughly, and then wipe all surfaces to be painted with mineral spirits, applying the mineral spirits with a paper towel. Wear nitrile gloves when applying mineral spirits, since nitrile can withstand solvents well. The mineral spirits will degrease the surface of the metal windmill, removing any oils that may interfere with the paint adhesion process. Allow the cleaned windmill to dry completely before priming.
Prime your cleaned and prepared metal garden windmill with an oil-based anti-corrosive primer specifically designed for weather-resistant metal painting. Since fine detail work is not necessary at this stage, you can use a disposable brush for applying the primer layer. Allow the primer to dry for 24 hours before painting the garden windmill. Keep the windmill in an enclosed, well-ventilated area while it is drying, to protect the wet primer from contamination by dust or dirt particles. Apply a thin initial coat of high-gloss oil-based exterior paint. If possible, use the same brand for both the primer and paint. Allow the initial paint layer to dry for 24 hours, and then apply the second coat. Keep the garden windmill protected from the elements for an additional 24 hours before moving the windmill back into your garden.