powder coat aluminum ???

Chi Town Runner

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Maybe a silly question but....
Can you powder coat aluminum?

I'm thinking of radiator shroud..
 

zyzzyx

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Yes. Powdercoat can be applied to anything that can survive being put in an oven and baked at around

400F. The aluminum would need to be perfectly clean and blasted so the surface is not shiny or slick.
As the particles melt and flow out, they form the surface on the part. Some parts will warp at 400F,
so it's always smart to have someone who has alot of experience.
 

peabodyracin

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A couple things to add to the discussion:

1) Don't go berserk blasting the aluminum. Being a soft material, too much pressure and/or too aggressive a media will leave the surface too rough to create the look I suspect you're after. Powder coating isn't body filler, so you don't want to be putting it on thicker than the mfr recommends to try and smooth out a rough surface. Glossy powders have a lot of flow agent added to get the powder to smooth out. On an irregular surface this causes the 'high' points to not be fully covered and makes for a rougher appearance.

2) Plastic media, , crushed glass, soda, etc would be what I recommend. We used a plastic media/crushed glass combination which worked very well, adjusting the pressure to the material being blasted.

3) Aluminum can be chemically etched as an alternative. That would require a shop with a good pretreatment system.

4) Powder mfr's are all pushing toward lower cure temp powders. It's unlikely a radiator shroud would require 400 degrees F to cure. We would typically run thinner aluminum like that at 350 F, sometimes even a bit lower.

5) If it's a used shroud that has seen a lot of service time, it's likely grease, anti-freeze and oil residue has collected in any areas where two sheets of aluminum overlap, under rivet heads, etc. When the part is heated up, if that's still there, it gets viscous and runs out onto the adjacent surface, ruining the appearance there. A good shop will know to preheat the part at least once after washing to try and make sure that doesn't happen.

6) Pay attention to the powder chemistry. Epoxies tend to offer the best chemical resistance. Here too, a good shop will know what to use.

Hope this helps.
 

topside

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I was told by a powdercoater that aluminum needs a bake cycle before it's coated.
Don't know if that's true, but worth asking about.
I've had 2 sets of wheels powdercoated - 1 set of steelies, and a set of aluminum OEM wheels - and won't do that again.
The steelies have rusted, and the aluminum ones would mar & scratch very easily.
I have wheels I painted 30 years ago that still look new.
 

peabodyracin

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I was told by a powdercoater that aluminum needs a bake cycle before it's coated.
Don't know if that's true, but worth asking about.
I've had 2 sets of wheels powdercoated - 1 set of steelies, and a set of aluminum OEM wheels - and won't do that again.
The steelies have rusted, and the aluminum ones would mar & scratch very easily.
I have wheels I painted 30 years ago that still look new.
Cast aluminum may require a pre heat to get any outgassing out of the way. Extruded stuff typically does not require this. The casting process can create small air pockets in the finished product, which heat up and 'out gas' during the heating process. The result is little spots that look almost like dirt in the finished coating. Really porous castings can outgas bad enough to leave bare aluminum showing. Old cast iron stuff is really prone to outgassing. If you really want to get your local coater excited, tell them you want to bring in a bunch of old house radiators to be powder coated, or better yet, an old cast iron bed frame. How do I know this......

We'd see a fair amount of the problem with imported (China) custom wheels. The second problem would be a chrome finish that's failing. We would end up chasing that with the blaster seemingly forever. US made wheels would not normally give us such trouble.

There are anti outgassing primers available, but that means painting the piece twice, adding cost and can result in too thick a final surface, particularly of concern on things like wheels that see every day use.

I would bet your steel rims started rusting where the center section meets the rim. This is a difficult area to get charged powder particles in to. If they're used rims, the area tends to be full of crap sandwiched between the two surfaces which is very difficult to remove completely. Your aluminum rims may have been inadequately cured, or were painted in a chemistry not real good at scuff/mar resistance. Most of the time a properly done powder finish is superior to a liquid one.
 

topside

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Yeah, I was unpleasantly surprised at the aluminum wheels: a buddy has had great luck with his, which were done by a different guy.
You're correct on the steelies, though they were clean wheels originally, and the guy blasted them before coating. They're also rusting on parts of the center sections. They've never seen salt or chemicals.
 

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