Preparing aluminum for painting is an important step. You will need to make sure the aluminum is free from older paint, dirt, dust and grime. It is vital to understand that paint sticks to rough surfaces. Dust or older paint will make the new paint job harder to manage and maintain. You may even see peeling on your new paint job within only a week.
Remove the old paint. If you are working with bare aluminum, skip to step 3. When the older paint is peeling, you can use a pressure washer or a hose with a strong nozzle stream to remove the excess paint. Spray the water at an angle on your aluminum. This should take off most of if not all of the older paint.
Use a sander, if not all of the paint came off with the water. If the area is small, sandpaper will work just as well as a sander. You will need a 50-grit sandpaper to remove the excess paint. This is a course paper designed for stripping and making the metal rougher.
Wash the aluminum. Use a long squeegee and get it moist with the hose. Add dishwashing soap to the squeegee and begin washing your aluminum. Use long strokes, scrubbing the dirt and grim off the aluminum.
Use the pressure washer or the hose to wash off the soap and excess dirt. Move the hose back and fourth over the aluminum to remove the rest of the soap and grime. Spend about 10 to 15 minutes on this step to make sure the entire soap residue is completely gone.
Air-dry the aluminum. This needs to be completely dried before you begin priming and painting your aluminum.