Anodizing Aluminum

Try your local university or college chem lab dispensary.

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.

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

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.–

Radiator shop?

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.–

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

"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.–

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.

;)

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

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.

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.

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…)

"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.–

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.–

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?

"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.–

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.

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.–

Bob, my question was: why do you need to anodize? The cans as supplied have a pretty robust surface treatment, being anodized and painted/dyed. Why remove this protection?

> There is seldom any paint or dye on the inside surface, so what are you ingesting?

Yes, there's no paint/dye on the inside. But there is on the outside of the can/bottle. When I drink from cans/bottles, my lips do tend to touch the outside surface. If the surface finish (be it paint or dyed anidizing) were toxic, I might ingest small amounts of this toxin.

I'm not paranoid about these sorts of things; the BPA scare didn't scare me one bit, and neither do the other regular scares about phthalate leaching from PET bottles re-used as water bottles. I'm fairly realistic about the tiny risks these pose, compared to all the other chemicals we're exposed to, and other life risks. However, the FDA are concerned about these sort of risks, so I'm pretty sure that they will mandate that any surface finish of drinks containers must be non-toxic. The press/public also seem to be unnecessarily concerned with these scare stories, hence the BPA panic and manufacturers clamouring to point out their BPA-free status, or changing their plastics.

My post was intended to be somewhat tongue-in-cheek, commenting on the irrational nature of these scares.

My point was: if the existing surface finishes are robust and non-toxic, what is the reasoning behind removing them, and thus needing to re-anodize the metal?

Kevin, I want to strip the paint off the outside surface so that I can get rid of the beer labeling, and then so that I can anodize the inside and outside surfaces to passivate them against corrosive attack by liquids.

I could leave the paint in place and just paint over it, but that would add weight, and the paint probably would not stand up to the heat of a hot fire.

If I do an initial anodizing job correctly, I can also use an anodizing dye on the outside to make it some desired color. "Miller Lite" is not a desired color to me.

–B.G.–

BG — have you considered glass bead blasting to remove the paint?

Well, no, I don't have a glass bead blaster. Nor do I have a sand blaster.

So far, methylene chloride paint stripper is having little effect. The only two things that are working are sandpaper and steel wool. The sandpaper is a bit harsh, and if I lean on it, I get little thin spots in the metal, or I get little kinks and dents in the metal. The steel wool is more gentle, but it takes about an hour to get most of the paint off one stinking can.

I may have to empty some more cans to make raw materials.

–B.G.–

Bob

Scotch bright them while they are full. And please let us know if you find a way to remove the inside lining. I have tried everything I can think of, and nothing seems to work. If you get the lining out, and hard anodize a beer can, you are really on to something.