Project 4: What to anodize?

January 25, 2011

Canteen set

The first thing I did when I discovered anodizing was to shop for some cheap aluminum thing that I could use for testing. I went to a local antiques store and found this Boy Scout canteen set. It has a cup, a pot, a plate, and a pan with an adjustable handle that holds everything together. However, before I could try it out in the anodizing rig my husband gave me something else to test:

Cap catcher

This is an aluminum cap catcher like you would hang under your bottle cap opener. He wanted me to try dying it red as a test for the local homebrew supply store. One fun thing about anodizing, aside from getting to dye metal colors, is that the anodization can be etched. This means that something metal like this cap catcher could be branded in a more visible way than just etching the metal itself.

So I tried anodizing it. Basically what you do is hang the metal object into a bucket of sulfuric acid with a current running to it via a conductive wire. When the anodization is done the metal is porous and will pick up regular laundry dye.

At least that is the theory. For this particular piece I was having no luck getting the anodization to work. It turns out that the cap catcher is coated in a way that makes the metal not conduct electricity. Since the electricity is a vital part of the process, the anodization didn’t work.

I hope my canteen set is the right kind of aluminum! Check back tomorrow to see my results.


  1. Can’t wait to see the results on this one. I couldn’t believe it when I saw you were going to anodize aluminium. I never thought of this being done by anyone except a large scale commercial operation

  2. You could, you know, test the electrical conductivity with a volt-ohm meter and if it doesn’t conduct try scraping off a bit so you could get a part that does.

    Of course, the coating itself would probably mess up the anodizing process too. 😦

  3. @Tanner, Yes, one can scrape one’s way through the sealant and get good electrical contact on the cap catcher–but as you say, the sealant will prevent the anodization as well.

    We can probably use some combination of solvent and mechanical effort to get the sealant off completely, but honestly I lost a lot of interest when it became clear it would be too much work to produce batches of them and sell them for a reasonable price.

    I haven’t broken out the ohmmeter (blew its fuse and haven’t replaced it yet), but the old canteen set looks like the right thing, and doesn’t have the improbable level of polish to it that turned out to be sealant.

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