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Natural Aluminum Finishes

#1
In preparation of painting my FT Sea Duck, I wanted a simple and effective way to produce a natural aluminum finish. Peter Sripol's method of sanding everything first produced excellent results; however, it is time consuming.

I evaluated three enamel spray paints with and without primer. For the primer, I used Zinsser BIN Sellac-Base primer. The three metallic paints all purchased at A.C. Moore are: Rust-Oleum 2X Metallic Aluminum (11oz for $6), Testors Gloss Metallic Silver (3oz for $6), and Champion Sterling Silver (8.5oz for $6). One caveat: the spray paint was room temperature and I sprayed outside on a sunny, January day. All three manufacturers recommend 70 degrees Fahrenheit; however, my better half does not appreciate paint fumes in the house. More details below.

I volunteered one of my FT Viggen noses for this test. I did not sand the waterproof foam board. I divided it into six sections: one for each paint brand—with and without primer. As mentioned above, I painted outside. The weather was warm for New England—sunny, 55 degrees Fahrenheit, 60% relative humidity, and southwest breeze at 9 mph. I kept all the paints at room temperature until going outside to spray. All applications were at 12 inches from the surface. One light (but thorough) coat was used for each test square.

I primed three of the squares with the BIN shellac and let it dry for 30 minutes per instructions on the can. I then painted two squares (primed and bare) with each paint brand. Rust-oleum on the left, Testors in the center, and Champion on the right. A peel test using blue painters was done at 30 minutes and then again several hours later. I took pictures from two angles and a short video of the primed and bare samples.

We'll start with bare foam board without primer:

no-primer-1.jpg

with-primer-2.jpg


No primer from another angle. L to R: Rust-Oleum, Testors, and Champion

And now a video of no primer:


The bare foamboard did better than anticipated. All three brands look decent enough; however, the Champion (far right) was, in my opinion, the most metallic-looking.

Moving on with shellac-based primer:

with-primer-1.jpg

no-primer-2.jpg



With primer from another angle. L to R: Rust-Oleum, Testors, and Champion

And a video:


Try to disregard the blemishes on the primed samples. I dropped my paint shield on the wet paint by mistake. The primed surfaces are deeper in color than represented in these images. Again, I give the nod to the Champion brand.

Finally, a peel test using blue painters tape. The top strip was done 30 minutes after painting. The bottom was several hours later. We'll start with no primer:

no-primer-peel-test.jpg


Champion (far right) is the clear winner here. Testors comes in last even though it is the most expensive paint in this test.

And now with primer:

with-primer-peel-test.jpg

I was very surprised with this result. The primed surfaces did very poorly after drying for several hours. Not sure if the colder than recommended temperatures played in this or not.

Conclusion: The primer helped a little in color quality but made adhesion far worse. Maybe this would be different on a warmer day. All three paints looked fine to me. They all had a nice color and sheen. However, I'd give the edge to the Champion Sterling Silver without primer for its superior adhesion to waterproof foamboard. I'll likely repeat this test in warmer weather to see if the results are different.

I look forward to hearing what others have done to create a natural metal finish on their planes.
 
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willsonman

Builder Extraordinare
Mentor
#2
Cure time is everything. I let all of my painting cure out for at least 24 hours. Even my acrylic work, which is dry to the touch in just a few minutes, is cured for 24 hours before handling.
 

PsyBorg

Wake up! Time to fly!
#3
Metallic paints are also known for having very poor adhesion. I can still remember my mothers old regency 98 back in the day with the silver paint flaking off the hood in sheets. Even the clear coat over it would not bond properly.

Personally I would go with the Testors brand if you want an "Aluminum" finish. The Champion looks more like a chrome at least to my eyes at 2 am hehe.
 

willsonman

Builder Extraordinare
Mentor
#4
Yes, that is also true. Metallic paints ARE known to not adhere well. I've done metallic undercoats before. Once cured, I applied an olive drab over coat and dragged steel wool across the surface to strip little pits of the olive to reveal the metallic finish. This is a weathering technique. The problem was that if I pushed too hard or did it too frequently the silver would peel up as well and it was far easier to remove.
 
#6
Thanks for the post. whenever I paint it seems like all I get is fuzz, never a smooth finish like this. How do you beat the fuzz?
 
#7
Thanks for the post. whenever I paint it seems like all I get is fuzz, never a smooth finish like this. How do you beat the fuzz?
I've never had the fuzz problem so I'm not sure what the issue may be. This is my first time painting the FT water proof foam. I didn't do any surface prep or priming prior to applying one coat of metallic silver. Before the water proof foamboard, I always Minwaxed the white DTFB and that produced good finishes as well. Sorry I can be more helpful with a solution.
 

TooJung2Die

Well-known member
#9
I saw another spray paint test with similar results. He used common white Adams foam board. The surprise winner for adhesion was untreated foam board. The loser in the adhesion test was Minwax treated. The waterproof qualities of spray paint alone was on par with Minwax treatment before spray paint Adams foam board.

I never tried spray paint on Adams because I heard the solvents dissolve the foam. Now I'm going to have to try it. Light coats.
Jon
 

TexMechsRobot

Posted a thousand or more times
#10
I saw another spray paint test with similar results. He used common white Adams foam board. The surprise winner for adhesion was untreated foam board. The loser in the adhesion test was Minwax treated. The waterproof qualities of spray paint alone was on par with Minwax treatment before spray paint Adams foam board.

I never tried spray paint on Adams because I heard the solvents dissolve the foam. Now I'm going to have to try it. Light coats.
Jon
If you spray in light coats, the propellant will evaporate in the air before it reaches the foam and the paint will stick. It has to be done in light coats though. Think 12" or more from the surface and it should take 3-5 coats to cover it.
 

JimCR120

Got Lobstah?
Site Moderator
#11
Home Depot and Lowe's were kind in allowing my son and I to test some spray paints on FFF I was going to buy. All of the spray paints failed when sprayed directly onto the foam. The only ones I've seen that were foam safe were special foam safe paint from Testors. It was a mini spray can and ~$6. Too much imo.

The foam can be significantly protected by some other layer such as paper (DTFB), plastic film (FFF), or another coat of non-harmful paint.

Brushing on paint from a can can reduce the cost and increase the options.

Another avenue to consider would be airbrushing. There is more initial cost but the results are pretty sharp. I hope to get into this.
 

TooJung2Die

Well-known member
#12
Another avenue to consider would be airbrushing. There is more initial cost but the results are pretty sharp. I hope to get into this.
That's what I've been doing. Bought the cheapest Harbor Freight airbrush, about $8. I already had an air compressor. Works great with Walmart Apple Barrel acrylic thinned with Windex and dries to touch in minutes. Adhesion? Good enough. Now I wish I had bought a better airbrush so I could do some airbrush art. The cheap airbrush is only good for laying down paint. Warping and paper delamination are a big problem with acrylic paint if the foam board is not pre-treated with Minwax.
Jon
 
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JimCR120

Got Lobstah?
Site Moderator
#13
Hobby Lobby had one for ~$25 that was recommended by someone who spoke like he knew what he was talking about calling it good for beginners (me). The next one up cost a lot closer to $100 (more than I plan on spending).

What do you have for a compressor? I have a small one that I use to fill soccer balls that I would use if it could do the job.
 

TooJung2Die

Well-known member
#14
I have a Harbor Freight 8 gallon 120 psi compressor. I've had it for many years. As much as I need an air compressor it's been good. Read up on the HF Deluxe Airbrush. It's under $18 with a coupon and has good reviews. If all you want to do is spray paint the $8 basic HF airbrush will do a good job. I like mine. All you need is 30 psi to run an airbrush.