Help with Aluminum.

Or "Aluminium" for our British speaking friends.

I have an aluminum prop that I have has to shape by sanding. The sanding then had to be smooth so it wasn'y "scratchy", and now the aluminum has a fairly bright shine to it. I would like my aluminum to be dull. How does one go about doing this? I dont want to get it anodized, and even if I could, I cant - I just dont want it to be shiny. A friend suggested I paint it a "aluminum metal color" which would infuriate me due to the hundreds of other substances the prop COLD have been made from and then painted metal colored. I just want my pretty aluminum to look a little less pretty. If it were STEEL, I would leave it outside and it would dull and then eventually rust. Will polished aluminum "tarnish" in the same way? Is there something to accelerate the process with?

Thanks.

The internet is highly annoying. Google searching gives equal numbers of responses saying "Aluminum doesn't tarnish" as well as "Aluminum QUICKLY tarnishes".

Grak.

You might try sanding with different grades of sandpaper. For example, to give something a mirror finish you would want to sand with 600, 800, 1000, 1500, 2000, and then finish it off with a rubbing compound to buff it to a final shine. But to give something a matte finish you stop on a lower grit. So maybe you need to sand the whole thing uniformly with a lower grit than whatever you used to shape it?

I don't know about aluminum tarnishing. I know chrome will tarnish in a saline solution and nickel in pcb etchant solution or muriatic acid (pool cleaner) so you may want to try something like that. Use gloves, and a respirator if you decide to go that route.

Wait, scratch that. All you need is some good old anhydrous copper sulfate. I'm sure you have some in your medicine cabinet right?

Shocked

http://www.nontoxicprint.com/etchzincsteelaluminum.htm

Thanks, I will check that out. As for "roughing it up", I had thought of that, but I don't want visible scratches.

Just read the link... looks good. I'll go the to metal supply tomorrow and check out prices.

Thanks for finding that.

You don't necessarily get visible scratches, especially to the camera's eye. Theoretically you could get a uniformly matte surface using the right grit of sandpaper and the right grit of rubbing compounds after that but it might take some experimentation.

My only experience in this area comes from finishing a guitar and I got that link from a search on the reranch forum http://www.reranch.com/reranch/viewforum.php?f=1

If nothing else works, it's worth registering there and asking some questions because those guys know a lot about trying to age metal parts. Mostly nickel and chrome, but I'm sure somebody there has some experience with aluminum.

Another option if you're willing to pay a bit of money is to find some kind of shop that can bead blast it for you. Evidently this is like sandblasting but finer and less destructive? I dunno. It's worth a shot.

I asked on Yahoo Answers and someone suggested using steel wool. As it's the cheapest solution, I'll start with that and then try sandpaper, then maybe chemical etching. I don't have the funds to hire it out. Thanks so much for the great suggestions and links.

I have a metal garden pot, and it's corrosion is an odd powdery white substance - I would assume some sort of aluminum oxide, problem is it rubs off very easily, easier than rust. What about a slightly tinted matte varnish or poly-urethane?

I thought of that, but there are sections of the prop that need to be shiny and sections that need to be very dull. Kinda like a knife - the edge being shiny, but the body being dull. I think the varnish coating might be too obvious.

"Aging Aluminum" seems to be a decent Google search - but I fear it will achieve a REALLY OLD look as opposed to just a DULL look.

well, you could always pick up some aluminum items at a thrift store to experiment on, that way you won't screw up your prop. I think the steel wool/ fine emery paper might do it.

I just tried steel wool (found some under the sink - didnt think I had any). It worked PERFECTLY. I didnt have the accuracy to keep the shiny parts shiny, but I think I can more accurately SHINE than DEshine.

Thanks so much for the help guys. Very Happy

maybe too late, but 3M Scotch Brite green scouring pads work well for aluminum and other surfaces. It's not as abrasive as sandpaper or steel wool.

Thanks Leo, that was a popular answer on Yahoo Answers, but for my piece, the scotch brite didnt work very well. Or, more accurately, the results were too subtle. Thanks for the tip, though.

Hi Gage,

You could try hitting it with dulling spray or a matte acrylic spray. You can pick both of them up at a photo supply store or even Hobby Lobby. Use masking tape to mask the parts you want to stay shiny. It looks different dried than when wet, so you'll need to practice on something else until you get the thickness and look your after. I've used it on glass and plastic, but I've never used it on polished aluminum, so I don't know how well it works on it. I would go with something like that before doing something permanent.

As for aluminum tarnishing, it depends on the alloy. If you need it to tarnish, it will be made from an alloy that resists tarnishing. If you need it high bright, it will be made from an alloy which will take on a tarnish before you can walk it from one end of the set to the other.

Rat's.
Missed the post about the steel wool. Glad you found something that worked. If you get the chance, post a pick so we can how it worked out.