To prepare aluminum siding for painting, use a pressure washer to wash the siding with a solution of hot water, bleach and trisodium phosphate, then apply oil-based metal primer to the surface. Use a drop cloth to protect any plants around your working area from chemicals. This process takes a few hours to complete.Continue Reading
Pour a gallon of hot water into a bucket, and add a cup of bleach and a cup of trisodium phosphate. Mix the ingredients to form a uniform solution, and pour the cleaner into a pressure washer.
Switch off the power breaker that serves the exterior sockets to avoid electric shorts, and use a drop cloth to cover any plants near the building. Set the pressure washer to 600 pounds per square inch, turn the wand downward, and spray the siding with the cleaning solution. Use a ladder to access the upper parts of the siding. Let the siding dry thoroughly before proceeding.
Mix a gallon of oil-based metal primer with a pint of paint thinner, and apply a coat of primer to the siding. When the primer has dried thoroughly, the siding is ready to paint.