Small punctures or cracks in aluminum siding can be filled with goodquality caulking compound. Cleaning aluminum siding Siding that is 15 to 20 years old may chalk, or discolor. Apply a piece of masking tape to the siding; then pull the tape off. If a-whitish residue remains on the tape, the siding is chalking. To remove chalking or corrosion, scrub the siding with a wire brush and detergent solution. Carefully rinse the surface and let it dry. Rent a pressure washer for large areas.
If the cleaned surface is in good condition, give the siding a coat of clear metal sealer or diluted varnish to prevent the chalking from recurring. Painting aluminum siding If the surface of your siding is in poor condition or if you want to change the color, first clean the siding. Then brush on two thin coats of an oil- or latex-base metal primer designed for bare aluminum. Using fine sandpaper, feather, or sand smooth, any ridges or irregularities. Finally, add a thin top coat of an acrylic paint with a flat or semigloss finish.
Because aluminum expands and contracts with changes in the weather, make the paint coats thin to avoid cracking. For some paints you have to apply an intermediate bond coat. Check with your paint dealer.