The most important aspect of painting an aluminum porch is preparation and priming. Good preparation and priming will create a surface to which the paint will adhere. Additionally, good preparation will prevent paint from blistering as it dries because good prep removes all dirt, loose paint and moisture. With the prep done correctly, either an oil-based or high quality latex paint will get the job done nicely.
Preparation
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The first stage of prep is the removal of old, loose paint. Use a paint scarper to break away sections of loose paint from the aluminum. Sweep away all paint chips off the porch when done scraping. Sand the sharp edges of the old paint that won't scrape off to give the paint job a smooth finish. Wash the entire porch with a sponge, water and good quality, powdered soap and scrub vigorously. Spray the porch off with a garden hose and allow it to dry for several days. Prime and paint the porch on a sunny, dry day.
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Primer
The best primer to use for aluminum is a thinned, oil-based metal primer made up of 1 gal. of oil-based, metal primer and 1 pt. of paint thinner. The primer creates a barrier between the oxidizing aluminum and finish paint that ensures a longer-lasting, more-durable paint job. Furthermore, "Hytechsales.com" argues that primer provides a "tooth" for the finish paint which will allow it to adhere better. Apply one coat of primer to the entire surface of the porch on a dry day and allow to fully dry by following the drying time chart on the side of the paint can. Apply two coats of finishing paint within 48 hours of applying the priming coat.
Oil-Based Paints
Oil-based paints are difficult to work with because they are difficult to spread and clean up. Furthermore, they have a longer drying time compared to latex paint. However, oil-based paint has the most durable, hard and longest-lasting finish of all paint. This paint is perfect for a high traffic area, such as a porch because of its durable finish. Most oil paint has a glossy finish which makes it more washable than water-based paints. Apply the paint on a very dry day and allow it fully dry before applying a second coat.
Latex Paints
Latex paints are a water-based paint that makes up 80 percent to 90 percent of all paint sales, according to "HouseAndHome.com." The paint is exceptionally easy to work with and clean up. Latex paints also have a quick drying time. Furthermore, it's available in multiple finishes from flat to high gloss. A high quality gloss finished latex paint will work perfectly well on well-prepared aluminum surfaces. The gloss finish will make the porch easier to clean. For an aluminum surface, high quality latex enamel works best. Enamel means that there is higher concentration of resin in the paint which will ensure a longer last and more durable finish. Apply latex paint on dry day and allow it completely dry before applying a second coat.