Aluminum finish for play structure?

Hi. I've designed and built a unique treehouse/swingset/climbing structure for my children. It has a couple of aluminum components,
such as a "high bar" made of aluminum pipe. The problem is, when the kids hang on the bar, the aluminum makes their hands black. I've tried rubbing it down with fine steel wool, cleaning it with alcohol, and rubbing it with an automotive polishing compound. Only helped a little. Is there a way I can treat the aluminum to solve this problem - either a different way of cleaning it or some sort of coating I can apply? It would have to stand up to the elements and not flake or chip off. I think an ordinary paint would likely flake off at some point, possibly creating more of a hazard to the kids than the aluminum rubbing off on their hands. Any suggestions? Thanks!
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powder coat. you'll have to take it somewhere to do that.

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Spray on clear coat. Wipe down with denatured alcohol or Acetone before coating. Michelle
Todd Rose wrote:

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Michelle, can you be more specific about what kind of clear coat you're thinking of, and where I might get some? I posted this same question on another forum, and someone suggested a type of coating available at auto paint stores for coating aluminum wheels. Is that the type of thing you mean? Everyone else suggests either powder coating or anodizing - options I will certainly consider - but if there's a product I could spray on myself that would be plenty durable, it would be quicker and less costly. Thanks!
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I used something years ago to coat my Tv antenna. I cannot find it anymore. I looked on the Krylon website and the have an Exterior "paint" called Crystal clear. Acrylic Flat, Acrylic Gloss and Acrylic Satin. Take your pick. Michelle
Todd Rose wrote:

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Todd Rose wrote:

Todd:
    You could send the pieces out to be anodized. Even color anodized if you wish. It'd look nice and probably outlast your kids.
-- BottleBob http://home.earthlink.net/~bottlbob
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Cleaning it will not fix the problem as it's not a matter of it being dirty per se. It's the aluminum oxide that's rubbing off the surface that is giving your children black hands. When you clean and polish it, you are removing the surface oxidation (and I'm betting that the waxes/oils in the polishing compound is retarding their return), but it will continue to come back.
Here are your options from best (most durable) to worst (which happens to also be the order of expense):
1. Hard anodize the aluminum. This is basically an electro-chemical oxidation of the surface of your aluminum. This induced oxide layer is extremely strong and durable and will not rub off or even scrape off. (For example, check out the dark gray surface of a Calphalon pot.) What's nice about hard anodizing (besides its durability) is that it can be done in a way that is not glossy slick (good for pull-up bars). Also, it can be colored which would look very cool.
2. Powder coat. This is much more durable than paint, but it will eventually get nicked and scratched. It will also tend to be more slippery.
3. Prime and paint. This probably won't last too long.
Of course, you could always wrap the bar in an adhesive athletic tape or similar product. This will stop the black hands, slightly cushion the bar, and give a much better gripping surface. This is what we had on the pull-up bars at the crew boathouse when I was in high school.
- Michael
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Lots of aluminum airplanes sit outside painted =)
Zinc chromate primer is the key, and a quality enamel or epoxy finish

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Yes, but you're talking about industrial finishes. These are not commonly available, very expensive ($100 or more per gallon), difficult to apply (and more difficult to clean up after), and highly toxic (not ideal for young children's play equipment). I was referring to the paints commonly available at hardware and paint stores.
I think powder coating would be the best compromise between cost and durability. And powder coating is non-toxic (and good for the environment, if that's important to the original poster).
- Michael
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Many thanks to Charles, Michelle, BottleBob, Dan, and Jon for your replies. Special thanks to Michael for your very thorough and thoughtful input. I haven't yet coated the bar, but I've been learning a lot about anodization and powder coating, who's available in my area to do these processes, and the associated costs, and will make a decision soon. Thanks again.
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I think that ordinary primer and then paint is likely to last for several years. And is easily touched up at that time. It should not be a hazard to your children. Check the label for ingredients. Lead has been banned since about 1977.
Dan
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