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Anodizing Aluminum
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Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Anodizing Aluminum on 06/24/2011 15:41:11 MDT Print View

Some of us build our own lightweight gear out of recycled aluminum beer cans, cat food cans, and such. Sometimes these get used as alcohol stoves, sometimes as cook pots, and sometimes as water boilers. In many cases, the aluminum metal is very thin and flimsy, and once the paint is stripped off or sanded off the aluminum, sometimes the metal surface is a bit porous.

It would be nice to anodize the aluminum to harden, smooth it, and passivate it against attack by corrosive liquids. I have just about everything I need to anodize some aluminum except for the one important item, one to three liters of concentrated sulfuric acid. I can buy it online, but the stinking shipping charges for Hazmat are several times more than the actual cost of the acid. Of course, the acid will be diluted for use. I'm trying to buy it locally.

I'm told that auto battery wholesalers have the stuff since they receive batteries dry from the factory, and they dilute the acid and fill up the batteries before sale. However, I have not found any such place that actually offers it for sale.

Any suggestions among the DIY crowd? Where did you buy your sulfuric acid?

--B.G.--

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Anodizing Aluminum on 06/24/2011 15:51:01 MDT Print View

Try your local university or college chem lab dispensary.

Josh Leavitt
(Joshleavitt) - F

Locale: Ruta Locura
Acid on 06/24/2011 16:20:40 MDT Print View

Find a full service auto shop, or alternative(solar,wind)energy dealer. I use to get mine from a battery wholesaler, until they would no longer sell it to me.

Al Nichols
(everready) - F

Locale: Sh!^^% Ohio
Anodizing local or ship it? on 06/24/2011 16:28:08 MDT Print View

Wouldn't it be easier to just find a shop that does anodizing and take/ship your items to them??

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Anodizing Aluminum on 06/24/2011 16:29:02 MDT Print View

I have no relationship with any local college chem labs, and I have not yet found anybody in the battery business who offers acid for sale. I think they are worried about liability, judging by the look on their face.

I can buy small containers of pre-mixed motorcycle battery acid. However, the cost per volume is high and the concentration is low.

--B.G.--

Joe Clement
(skinewmexico) - MLife

Locale: Southwest
Anodizing Aluminum on 06/24/2011 16:30:34 MDT Print View

Radiator shop?

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Anodizing local or ship it? on 06/24/2011 16:31:32 MDT Print View

Yes, there are metal shops that will do anodizing, and that makes it easy. Unfortunately, that is also the most expensive method, by far. They know that it costs money to put all of the ingredients together for anodizing, so they are profit-driven. Plus, that would kind of defeat the DIY idea.

--B.G.--

Brendan Swihart
(brendans) - MLife

Locale: Fruita CO
Re: Re: Anodizing local or ship it? on 06/24/2011 16:47:45 MDT Print View

speaking of looks on their face, imagine taking an empty foster's can into a metal shop and asking them to anodize it...

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Anodizing local or ship it? on 06/24/2011 16:50:37 MDT Print View

"speaking of looks on their face, imagine taking an empty foster's can into a metal shop and asking them to anodize it..."

And, worse yet, an empty Miller Lite aluminum bottle!

(Oh, the shame of it...)

--B.G.--

Javan Dempsey
(jdempsey)

Locale: The-Stateless-Society
Re: Re: Re: Re: Anodizing local or ship it? on 06/24/2011 23:38:10 MDT Print View

In the Bay Area that might get you shunned Bob, but in the SE, you'd probably get your anodizing for free. Especially if you could supply the rest of the case un-emptied.


;)

Don Meredith
(donmeredith) - F

Locale: SouthEast
Anodizing on 06/25/2011 07:03:01 MDT Print View

You can usually get pretty concentrated sulphuric acid as a plumber's supply. As I recall there's a product called Clobber or something like that that is 93% sulphuric. A local hardware store (not the big boxes) or industrial supply house should be able to help you.

DM

Josh Leavitt
(Joshleavitt) - F

Locale: Ruta Locura
Anodizing on 06/25/2011 10:28:26 MDT Print View

Bob

When you get your acid all worked out, here are a few things that have worked well for me. Heavy guage aluminum ground wire from radio shack, its affordable, and works for everything on the anode, and cathode side. Cathodes: if you need lead for cathodes, let me know, I have ~100+lbs I can share for a reasonable price. If you want/can melt your own lead down, I have some in "chip" form(cut on a lathe)that came from a large copper cored cathode(crome plating). I can share this really cheap. Ziplock bags: buy some good freezer bags, the sandwich size. You will get better results if you can keep the temps in check. I used ice in ziplocks, with lead weights to hold it down in the solution. Rit fabric dye: save your self some money and go with the Rit, I found that it worked as well as anything. Keep you dye bath temps high, but not boiling, and give it some time in the bath, regardless of the dye used. For uniform semi dull finishes, you can etch the surface of your parts with muratic acid from the harware store. Anodize removal: Red Devil lye, be careful, this is way more nasty than the anodizing process.

Chris Hanson
(ChrisHanson) - F

Locale: Eastern Wyoming
Red Devil Lye on 06/25/2011 10:34:31 MDT Print View

You might have trouble getting the lye too. I braintan hides and use lye as a "bucking solution". Since it is used in the production of meth, most stores have pulled it off their shelves.

Kevin Beeden
(captain_paranoia) - F

Locale: UK
re: muriatic acid on 06/27/2011 11:37:58 MDT Print View

muriatic acid, aka hydrochloric acid.

One question that comes to my mind is: why take the paint off in the first place? Cosmetic reasons, or other concerns?

I'd concluded that the dyes used for drinks cans are very likely to be non-toxic, given that you do contact the can when drinking from it, and, given that drinks such as cola contain phosphoric acid, you are likely to ingest some dye residues. Given the big fuss over BPA, it's likely that anything toxic on a drink can outer would be likely to cause a bit of a storm... (let's not think about all the grubby fingers that have handled the can in the distribution chain; we all wash our cans before we drink from them, don't we...)

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: re: muriatic acid on 06/27/2011 11:58:21 MDT Print View

"One question that comes to my mind is: why take the paint off in the first place? Cosmetic reasons, or other concerns?"

Apparently anodizing will work very poorly or else not at all if paint is left on the aluminum surface. There isn't much point in anodizing the aluminum if I am going to get only part of it done.

Dyes used for drink cans... I have no idea what you are talking about. Drink cans and bottles are normally painted, but that is on the outside surface. There is seldom any paint or dye on the inside surface, so what are you ingesting? You sound like you are living up to your nickname.

--B.G.--

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Anodizing on 06/27/2011 18:01:25 MDT Print View

I finally found an industrial distributor that stocked big box-packs of Exide battery electrolyte. I assume that it has already been diluted by 3:1.

The local Radio Shack store never has anything, and big electronics store had no aluminum wire at all, nor does Home Depot stock it. Lowe's hardware had one big spool of aluminum wire, so they whacked off some feet of it for me. I may have to pull out one strand of that. Actually, I need to scrounge up some small gauge aluminum wire to put through a small hole for a small part. I also got some aluminum angle to make one electrode.

Some methylene chloride paint stripper might work for preparing the aluminum part.

Gee, this may become a one-man Superfund site before I get done with it.

--B.G.--

Tim Zen
(asdzxc57) - F

Locale: MI
Re: Re: Anodizing -- Aluminum Cables on 06/27/2011 19:28:28 MDT Print View

BG -- I think the cheaper jumper cables are aluminum.

Have you figured out how to dispose of all them chemicals when you are done?

I know you want to do it yourself, but have you checked with your local custom car shop? I guess the custom cars are not common in your area (as they are in my area) -- maybe inland?

Edited by asdzxc57 on 06/27/2011 19:32:29 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Anodizing -- Aluminum Cables on 06/27/2011 19:42:56 MDT Print View

"Have you figured out how to dispose of all them chemicals when you are done?"

WHAT CHEMICALS?

Well, new dilute sulfuric acid can be kept for car battery purposes. Used acid can be neutralized with baking soda and water.

I will have to look up the methylene chloride MSDS and see what to do there.

Cheaper jumper cables may be aluminum, but right now all I need is some small gauge stuff.

Right now my problem is that the methylene chloride is not touching the paint on the aluminum bottles, like less than 1% dissolving. It must be good paint.

--B.G.--

Murray Peake
(mpeake) - MLife
Substitute for Sulphuric acid on 06/27/2011 19:51:57 MDT Print View

You might be able to substitute sodium bisulphate ( sodium hydrogen sulphate) for sulphuric acid. I bought some from a swimming pool shop for lowering the pH of the pool.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Substitute for Sulphuric acid on 06/27/2011 19:58:22 MDT Print View

I'm not sure exactly which acids can be used for aluminum anodizing, but sulfuric acid is the most widely mentioned acid, partly because it is one of the most powerful. The guys who do this a lot are seeking methods to speed up the whole operation, so they are using heaters and high-power DC supplies. That's nice, but I don't need to speed up my operation. I'm just experimenting on a small scale for now.

If I can't get the paint stripped off the Miller Lite bottle, that will put a knot in things.

--B.G.--