Is one coat of paint sufficient for my aluminum siding?
This question was asked to me during a recent estimate for the renovation of a Church House that sheltered the Pastor. The siding was a faded white with the finish showing obvious signs of wear and breakdown. The estimate request was to repaint the siding white again.
After about 20 years or so, aluminum siding will start to lose its shine and the finish will breakdown and become chalky. This will give dirt and mildew a perfect place to call home. The obvious solution for this is to apply a fresh coat of paint to revive your homes curb appeal, but before you do so make sure the proper steps are taken.
Cleaning the siding should be your first step. Bleach, water, and TSP is a good cleaning solution for this project. After the cleaning is accomplished, rinse well with clean water.
Chances are that all of the chalkiness did not go away and when you run your finger across the surface you will pickup some of the powder. In order to create a good bond between the paint and the chalky surface you will need to use an additive, such as E-B Emulsa Bond, with your finish paint.
E-B Emulsa Bond is made by Flood and improves the adhesion to exterior water-based coatings to chalky wood, masonry or aluminum surfaces.
E-B Emulsa Bond Technical Data Sheet states that "If the desired appearance is not achieved in one coat, a second coat of paint WITHOUT E-B Emulsa Bond should be applied."
So on the Church House, where the existing color is white and they want to paint it white again, one coat just might work on the coverage end of things but to get the most out of a paint job, I would always recommend two coats of premium exterior paint.
For more information on the subject you can visit one of my previous blog posts: Can you paint aluminum siding?