It is easiest to remove foam insulation from aluminum before it has had a chance to set and dry. When the foam insulation is still wet, it can be simply wiped away and cleaned with a mild detergent. Foam insulation that has set and dried requires more drastic cleaning measures to remove.
Things You'll Need
Protective respiratory mask
Non abrasive sponge
Put on protective gloves, protective goggles and a protective breathing mask prior to cleaning the aluminum to minimize the risk of skin, eye and respiratory irritation.
Saturate a non-abrasive sponge with acetone. Rub the aluminum with the saturated sponge to spread acetone over the foam insulation that you wish to remove. Regularly pour more acetone onto the non-abrasive sponge as needed. Apply a plentiful amount of acetone to the area to soften and dissolve the foam insulation. Be aware that the acetone may harm any paint or other finish that has been previously applied to the aluminum.
Fill a bucket with soapy water. Use a few squirts of a mild detergent to make the soapy water.
Pour the soapy water over the aluminum and scrub the surface using a non-abrasive sponge until the foam insulation is removed. If the foam insulation does not come off, try applying more acetone. If the foam insulation is not removed after a couple of attempts, an abrasive sponge can be used. Do note that an abrasive sponge will permanently scratch the aluminum surface.
Spray the aluminum with a garden hose to remove the soapy water.
Touch up any damaged paint or other finish, if the acetone caused damage.
Apply a coat of car wax to the cleaned and dried aluminum using a clean cloth to help protect the surface from further damage. The car wax provides a protective coating that protects the aluminum from damage from weather elements. The wax also helps stop debris such as foam insulation from sticking to the aluminum. To wax the aluminum, apply a small amount of wax to a clean cloth. Working on a small area of at a time, rub the wax into the aluminum surface using a circular motion. Wipe off excess wax with a clean cloth before moving to the next area.
Acetone can damage paint or other finishes. An abrasive sponge can permanently scratch aluminum surfaces.