Problem w/painting aluminum

1877 Views 9 Replies 6 Participants Last post by cephius, Dec 2, 2008

Ray Dunakin

Discussion Starter · Nov 29, 2008

The roof of the old stone cabin I built a while back was shingled with bit aluminum, embossed to look like flattened tin cans and other random pieces of scrap metal. The aluminum came from soda cans, and was heated with a torch to burn off the coating and make it softer so it would be easier to work with. After the individual pieces were glued to the roof, I painted them with a mixture of Floquil roof brown, rust, and gunmetal. Rustall and other weathering solutions were added to finish the effect.

Unfortunately, the paint is now flaking off! I have two theories as to the cause:

1. The metal wasn't clean enough after being torched, and may have had some sooty residue that prevented proper adhesion of the paint; and/or...

2. Floquil paint isn't flexible enough to handle the expansion and contraction of the aluminum.

Anyway, I now have to scrub off as much paint as possible using a small wire brush, so that I can properly repaint it. I'm considering using some type of acrylic based paint this time rather than Floquil.

Comments/suggestions?

Update: After scrubbing with a wire brush, I'm more inclined to believe that the adhesion problem was mainly due to tarnish/soot/whatever on the surface of the aluminum. In some areas the paint comes right off leaving a shiny surface, in other areas it resists even vigorous scrubbing. I've also found that some of the "shingles" are coming loose for the same reason.

I'm also thinking that in future, in addition to carefully cleaning the aluminum, I might also give it a brief acid bath to etch the surface a little.

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Roland Seavey

· #2 · Nov 29, 2008

Ray,
Alum. must be primed with a special alum. primer. It is a greenish yellow stuff. has a spicific name which I can't remember right now, been too long away from doin sheet metal on aircraft. Try an auto body paint store.
Roland

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R.W. Marty

· #3 · Nov 29, 2008

Ray,
Use a zinc chromate primer before painting.
Rick Marty

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Ray Dunakin

Discussion Starter · #4 · Nov 30, 2008

Is that something that can be brushed on? It might be a bit difficult to mask off the rest of the roof.

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altterrain

· #5 · Nov 30, 2008

I have never had a problem with using Rustoleum spray paint on aluminum. I have never tried brushing on anything though. You could try spraying some paint into a paper (not plastic!!!) cup and then brushing it on.

-Brian

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Richard Weatherby

· #6 · Nov 30, 2008

I have been cooking beverage cans for years. The interior coating turned a great rusty brown and soften the aluminum.
I install the aluminum with the interior side of the can facing out. The painted label never really comes off.
(The hopper underneath is painted with acrylic craft paint. It is not exposed to the sun and would be difficult to get to later.)

The Broken Heart Coal Tipple was original displayed in the golden brown of the cooked coating on the cans.
The Stamp Mill was placed outside in a similar fashion, then I tried sprayed and brushed paint finishes which tended to flake off. I tried wire brushing it off.
Actually, I finally found that leaving the buildings outside for six months, allowed the can's coating to weather off and return to the original shiny aluminum.
I then discovered "Modern Options - Sophisticated Finishes" - Rust kit which contained a primer/sealer, iron metallic finish, and an activator.
The 3 ingredients are inseparable. The primer is essential to proper bond. The metallic finish contains real iron filings in the paint. Then it really does not rust until you apply the activator. The sooner you apply the activator the "orangey" the rust. But if you wait too long (days). it will be difficult to get the right rust. Then leave it outside for the ultimate rust from the rain.

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Ray Dunakin

Discussion Starter · #7 · Nov 30, 2008

I tried the Sophisticated Finishes "iron" and "rust" solutions today, and I'm impressed. In two simple steps I got results that look almost identical to the meticulously hand-painted simulated rust I'd applied previously. The iron solution goes on kind of thick and requires some effort to get the lumps smoothed out, but it still allowed most of the embossed details to show.

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Roland Seavey

· #8 · Dec 1, 2008

Thanks Marty,,
Thats the one I was trying to remember
Roland

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altterrain

· #9 · Dec 1, 2008

Posted By Ray Dunakin on 11/30/2008 5:48 PM
I tried the Sophisticated Finishes "iron" and "rust" solutions today, and I'm impressed. In two simple steps I got results that look almost identical to the meticulously hand-painted simulated rust I'd applied previously. The iron solution goes on kind of thick and requires some effort to get the lumps smoothed out, but it still allowed most of the embossed details to show.

I have not tried them yet on a large structure but I usually thing the the iron solution a bit with water. You have to be careful no to thin it too much as it will effect adhesion.

-Brian

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cephius

· #10 · Dec 2, 2008

I've been using the same product on plastic. Like the smoke stack and hand rails on a caboose. Makes quite a difference in the model.

Dave

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