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Anodizing Aluminum Coils
(Overview)
Article © MAIL User: MeTri

How to anodize aluminum.


I don't see much point in duplicating the excellent full colour instructions I followed to anodize aluminum rings (see below for link), but this is an overview of what I did.

Overview of procedure and materials required.

- plastic container (has to be big enough to hold the coils, some acid and a piece of lead.)

- sulphuric acid

- a piece of lead (I used a bunched up piece of lead solder for stained glass windows, but any lead will work). This will the cathode (negative terminal)

- aluminum to anodize (positive terminal / anode)

- car battery charger

Basically we're making a battery and we're using a piece of lead and the aluminum coils to do it (rings are possible, but coils are much easier).

So first you have to add the acid to the container. Likely you will be buying more concentrated acid than you need, so we have to dilute it. ALWAYS add acid to water, NEVER the other way. Serious injury can result. Specific gravity of the desired acid/water mix is 1100. If you use battery acid, mix 50/50 with water.

So we now have a plastic container with some acid in it. Put the lead in so that it hangs from one side of the plastic container. Place the aluminum coils on the other side of the tank.

We have to connect the battery charger to the aluminum (+) and to the lead (-) . Please ventilate the area as some unpleasant gasses are formed in this process. Now turn it on. The lead will bubble, as will the aluminum. Make sure to watch the amp gauge on the battery charger. Too high an amperage means you have too much surface area on your aluminum. Try removing a few coils and try again. When the reaction slows, remove the coils, soak in water with a dye (140 degrees F) and then boil for 20 minutes. The dye is optional. Anodizing aluminum gives it a non-oxidizing coating making it scratch resistant.

This is not meant as a complete how-to guide as the attached link is amazing with pictures for each step. What I did want to explain is that coils have a lot of surface area, and with a small battery charger, I was able to do 3 coils in about 20 minutes. And you don't need a bunch of fancy equipment. Remember to wear safety goggles when working with chemicals.

For full colour pictures please see the below page on anodizing aluminum car parts. This is a very detailed description and should help you make nicely coloured coils.
http://www.focuser.com/atm/anodize/anodize.html
Original URL: http://www.mailleartisans.org/articles/articledisplay.php?key=213