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susnpb02
Painting alumium

Rather than replace it, we've decided to paint the existing porch enclosure on the back of our house (west facing on flat terrain with large trees in yard. Summer storms do blow at the porch). The enclosure is made of shiny aluminum, never before painted. We want to paint it dark brown to match the gutters, trim and windows on the remainder of the house.

The enclosure is made up of twelve sections. Each section includes an upper storm window, a lower storm/screen, and a textured panel near the bottom which is approximately 3.5 square feet. Vertically, between each of these sections, is a fluted support.

We have several questions and would appreciate the help.

1. Several websites say that "most latex paints" contain ammonia and that used on aluminum, the oxidation of aluminum causes gas bubbles to form, get trapped in the latex, and then blister. We have purchased Sherwin Williams Duration Exterior Acrylic Latex for this job on the recommendation of the store clerk. I found an MSDS sheet on Duration paint and no ammonia is listed, nor is it listed on the can label. On shiny aluminum, is oxidation a concern? We intend to prime it and would like to know if we should use an oil-based primer to provide a buffer layer between the aluminum and any latex paint? Any other issues with paint choices for bare aluminum?

2. A person we know who did power washing as side work says that we would be wasting our time to power wash bare aluminum, unless we could find a power washer (unlikely) that heated the water. His recommendation is to use s hot water, a scrub brush and Dawn dish washing liqud. He also says to paint it as soon as it is dry. A website I checked said that it takes two days for aluminum to thoroughly dry. Any thoughts on power washing vs. hand scrubbing bare shiny aluminum and drying time for the job? I am especially concerned about thoroughly cleaning all the nooks and crannies in the window frames, fluted supports and textured solid panels at the bottom of each section.

3. What about sanding, before primer? Between primer and finish coat? What grade of sandpaper? Or some other way to abrade the surface for better paint adhesion?

4. Last question...we were hoping to use an air compressor sprayer to apply the paint. We have a Siphon-Feed Spray gun and a large air compressor. By what ratio should we thin the Duration paint? Or must this job be a brush job and if so, what can we do best to prevent unsightly brush marks everywhere?

Thanks. We don't want to make mistakes on this job because it is a real chore that we don't want to repeat...or make it worse than the shiny aluminum.

Tom
Re: Painting alumium

I won't try to answer all of your questions but I will give you my own experience. We live in a Queen Anne house built in the 1890s and all of the storms were aluminum. We washed the storms, abraided them with a fine grade sandpaper(150, 220) primed them with latex Zinser primer and then painted them with a latex paint. This was five years ago and all of the painted storm windows are holding up just fine.

ordjen
Re: Painting alumium

I have never had problems with painting mill finish aluminum with latex paint. Mill finish naturally oxidizes over time and will accept paint. However, you state that the aluminum is shiny. This leads me to believe you have an anodized finish on it. You must first break the shiny anodized glaze either by sanding or with an acid etching.

susnpb02
Re: Painting aluminum
ordjen wrote:

However, you state that the aluminum is shiny. This leads me to believe you have an anodized finish on it. You must first break the shiny anodized glaze either by sanding or with an acid etching.

Thanks. Based on your statement, the preparation seems more important than ever. Any thoughts, please, about the merits of power washing vs. hand scrubbing?

ordjen
Re: Painting alumium

susnpbo2,

Power washing the windows will certainly aid in removing caked on surface dirt, but will do little to otherwise assure adhesion. There are self-etching primers on the market which are designed to adhere to aluminum. Sherwin-Williams sells such primers. Auto paint stores also have such primers.

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