How to oxidize aluminum?

[bgordon]

This maybe a heretical question, but how can I oxidize aluminum?

I have a 1948 Boles Aero with a beautiful patina and I'm going to keep it like that for a long time. I am interested in fabricating an aluminum tongue box and thought it would be great if I could get the patina to match (or at least get closer) to that of the trailer.

I have read that brushing on/soaking it in a salt bath/paste for a prolonged time works. It seems like I could just keep my eye on it for the desired depth of oxidation.

I know that oxidation weakens the metal somewhat so I don't want to go overboard with this.

Thanks

[Eric H]

Salt paste looks to be the way to do it. I'd say to oxidize the box while not attached so you don't oxidize any other parts! :-)
The machine finish that comes on the aluminum stock will have some haze already on it. It will certainly not be as oxidized as the rest, BUT it will also not have the clear coat on it, so it should oxidize faster than the trailer (this assumes you still have a clear coat on your trailer).

[ROBERT CROSS]

Believe it or not I've had good luck getting a "satin" finish back on uncoated aluminum with green scotchbrite pads and WD40.
You might try it on a small piece, clean it with mineral spirits after treatment and let it sit, it may be close to what your after.

Got any pic's of what your trying to match?

Bob

[bgordon]

[Someday'59]

Let it sit on the back 40 for 50 years. (Oh, wait. I don't think that's what you meant.)

[Wabbiteer]

One of those accidental metal finishes that may be hard to reproduce especially since the metals are already installed. Light reading says you should consult a professional

[ROBERT CROSS]

Nope not close....

It might werk if you scotched the whole trailer .....NOT.

The lower unit did look a lot like what your trailer looks like now when I first did it.

Bob

[bgordon]

I'm not expecting to replicate the 50 yr old oxidation, but it would be nice to break in the metal a little bit. Other option would be to paint it black so it fits with the trailer a little bit, but it would be a shame to paint aluminum.

I really like the oxidation on the trailer, though it's broken up in a few spots where people (either previous owners or potential buyers) test polished it. It's a little bit of a security feature and also heightens the perception of the cleaner more modern interior.

[truckasaurus]

Maybe try a test on small piece first but something like a metal prep such as Alumaprep or muriatic acid might be what you're after for an even "finish".

[perryg114]

I am not sure I would use salt. I would try some sort of weak acid like vinegar and go from there. Practice on some scrap metal from the batch you used on your trailer. Different alloys are going to produce different results. Start with weak acids and get stronger ones like sulfuric and nitric acid and HCL (Muriatic).

Perry