How to Prepare Aluminum Siding for Paint

Aluminum siding has many great advantages over wood siding, but one common misconception is that aluminum siding will never need to be repainted. Paint will probably last much longer on aluminum siding, but all paint, regardless of what it is painted on, will eventually chip or fade when it is constantly exposed to the elements. Any metal can be difficult to paint, and that is particularly true with aluminum. The trick to having a nice paint job at the end lies in taking the time to do a good job in preparing the aluminum siding to be painted. This is largely a matter of cleaning the aluminum and using a primer coat that was designed for use on metal surfaces. As long as you follow these quick and easy steps, you should be able to prepare your aluminum siding for paint with no difficulty at all.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Stiff bristle brush
• Trisodium phosphate (TSP)
• Paint scraper
• Electric sander
• Exterior spackle
• Putty knife
• Primer for metal
• Paint thinner

1. Wash the aluminum siding thoroughly with a mixture of water and trisodium phosphate. It is a good idea to wear eye goggles and rubber gloves while working with this solution. Dip a stiff-bristled brush (wish a long handle) into the solution and use it to scrub the walls down.

2. Use a paint scraper to scrape away any loose paint. If this job proves to be especially difficult, upgrade that paint scraper to be an electric sander. When using an electric sander, work back and forth in long, broad strokes, until the paint has been removed.

3. Inspect the aluminum siding for any holes. If you encounter one, use a putty knife to fill the hole with a vinyl exterior spackle. If there are no holes, skip ahead to Step 5.

4. After the spackling has dried, use a piece of 100-grit sandpaper to sand the area smooth, so that it is flush with the aluminum siding. Be sure to wipe away any dust that forms as a result of the sanding, because having a clean surface is one of the most important elements to preparing your aluminum siding to be painted.

5. Apply an oil-based primer that was designed for use on metal. Many professional painters recommend thinning the primer down before using it, so that it will have better penetration into any previously existing paint that remains. To thin the primer down, mix 1 pint of paint thinner per 1 gallon of primer. Allow primer to dry completely before you paint the aluminum siding.

Tips & Warnings

• Do not worry if your siding gets scratches from the sanding process. A slightly rough surface actually has more surface area, making it easier for the primer, and therefore the paint, to adhere to the surface.