A good simple finish for aluminum

[Electrojim]

I'd like to address the brain trust here on the subject of finishes for a 'natural aluminum' appearance. A lot of your guys have some spectacular examples of small engine models, etc., and I'd like to find out how to keep that kind of look over the long term.

There's anodizing, of course, which can be done in colors and provides an aluminum oxide layer that is very hard and durable. But it's a relatively expensive process (although it can be done at home... don't try it, kids), is not good if you have pressed-in steel nuts or whatever, and does change the final dimensions of the part by a small amount.

Next is Alodine, or chromium-passivation of the surface. An alodine finish, either in clear or gold, resists oxidation and grubby fingers but isn't terribly durable. Yet it can be done easily in the kitchen sink. There are similar chemical treatments that target boat owners or car enthusiasts with aluminum wheels, but it's not easy to establish how good these are.

Beyond that I suppose there's wax and clear-coat paint sprays. What I'm wondering is how you guys keep your mill-finish parts looking good over time. I'm making parts for some sound recording gear and would like to retain a natural aluminum look to the project, but worry about how time takes its toll. Any and all ideas are very welcome. Many thanks!

[Conrad_R_Hoffman]

Depends on how durable you want it. Clear lacquer or enamel works. If the parts won't be exposed to cleaners or ammonia, I use a little know cheat- acrylic floor finish. They change the name frequently to keep you confused, but I think it's Pledge Floor Gloss at the moment. Some good info here- http://www.swannysmodels.com/TheCompleteFuture.html

[NP317]

I agree on the use of clear lacquer or enamel finishes.
Easy to do, and redo if needed.
Below is a picture of my locomotive at 12 years of age. I clear lacquer coated the brass when new, and have not touched it since, except to wipe it clean.
~RN

[John Hasler]

Elecrojim writes:
There's anodizing, of course, which can be done in colors and provides an aluminum oxide layer that is
very hard and durable. But it's a relatively expensive process (although it can be done at home... don't try it, kids),

Right. Stick with safe, easy stuff like casting metal and building boilers.

[earlgo]

Birchwood Casey made a product called Aluminum Black for the touchup of Aluminum. It is POISON containing tellurium dioxide, fluoroboric acid, nickel sulfate and copper sulfate. But it works and leaves a black finish. I never tried to use it on a large surface, it is mostly used for touching up scratches on gun telescope tubes or aluminum frames.
Just another unmentioned alternative. In fact, I don't know if it is still sold. You might check your local gun shop.

--earlgo

[Electrojim]

Thanks for those tips, guys. Yes, Birchwood Casey does still make the blackening for aluminum. Amazon carries it; $45 for a quart, plus they have 'Sharpie' type felt pens of the stuff too. Might get as small bottle ($8) to try on some things, but mainly I want a bright aluminum finish and may just go with lacquer, although there are exposed ball bearings and other stuff that would not want to get anointed. Other options are carnauba or similar wax, or the chemical-passivization finishes like Alodine, Everbrite, ShineSeal, AlumaGuard and Shark Hide. Those are all readily available and I might pick up one or two and give them a test... see what their effect is on press-in stainless nuts, roll pins, that sort of thing. Will report back with anything interesting. Thanks again!

[RSG]

While I have not tried it I'm told "PEEK" works quite well at protecting polished aluminum.

For myself I've had good luck simply polishing with green rouge. Some of the parts are exposed to outdoor eliminates for a few hours at a time and still look as shiny as when made. A small amount of buffing every year or so would maintain the surface no problem.