How To Anodize Aluminum

The purpose of this thread is to enable anyone who machines or processes aluminum parts to anodize them as a final finishing step. Anodizing provides aluminum with a hard, durable, scratch resistant finish layer that can be colored during the anodize process.

The process of anodizing is neither difficult, nor expensive, and can easily be undertaken by the home or small shop.

An overview of the process :

The machined and polished aluminum part is cleaned and degreased.
The part is placed in the anodizing tank and power is turned on.
The part anodizes for about an hour.
It is removed and rinsed with water.
If color is required, the part is now dyed.
The part is sealed by boiling.

If you want to anodize, you will need to gather the following supplies and materials.

1) A 12V car battery charger rated at 4A or better.
2) Some lead wire, like thick plumbers solder of the old lead type.
3) Some aluminum wire and sheet aluminum.
4) Battery acid (sulfuric) from an auto parts store or your mechanic.
5) Some clip leads or similar wires.
6) A glass or plastic container (dollar store)
7) Dye, sharpie markers, etc. for coloring.
8) A pot large enough to boil the finished parts in water.
9) A stove to heat the boiling pot.
10) Some kind of degreaser, like Mr. Clean, or blue glass cleaner.

You can use the 12V rail of a salvaged PC power supply, or any other type of around 12V supply that can give a few amps.

When ready to anodize, you will need to prepare the anodize bath. For my anodize tank, I got a pasta storage jar at the dollar store. It is glass, about four inches in diameter, and quite tall for anodizing battery barrels. Fill your anodize tank 4/5 full with water. Slowly add the battery acid from the auto parts place to the water to fill up your tank to about an inch from the top. This is your anodize bath. Now you need to prepare your negative electrode. This is made of lead. I use 1/8 inch dia. lead wire that was once used as plumbers solder. The sulfuric acid won't eat lead. Wind a flat spiral of lead wire that will fit on the very bottom of your tank, and leave a piece long enough to come up the side of the tank and fold over the top edge and down an inch or two on the outside. You will connect the negative lead of your power supply to this.

Next you must prepare the part itself for anodizing. Clean and degrease it carefully with a solution of Mr. Clean in water, or blue glass cleaning liquid. If any finger grease or waxy polish residues remain on the part, these areas will not anodize. Rinse in water after degreasing.

Once the part is clean, it needs to be connected to the positive supply. This must be done with an aluminum connector or aluminum wire. This is because the connection will be immersed in the acid along with the part, so copper or other materials cannot be used as they would react with the acid. This connection must be made to the part in an area that doesn't show as this connection point will not anodize. If your part has a threaded hole somewhere, you can use an aluminum rod with the end turned down and threaded to fit. For hollow parts, I use a u-shaped spring clip I cut and bend from sheet aluminum. For other parts, aluminum wire like MIG wire can be used. Always use a DMM to verify contact between your part and its aluminum connector. When the part is put in the anodize bath, part of the aluminum connector sticks up out of the acid so that the positive power supply lead can be connected via a cliplead. See the attached video about connecting parts.

Once the part is connected, it must be hung in the anodize tank so that it is fully submerged in the acid bath, and does not touch the negative lead electrode anywhere. Connect power supply negative to the lead wire and spiral coil you made and put in the tank, connect power supply positive to the part of the connector left sticking out of the acid bath. Turn on the power supply. You will see bubbles forming and rising as the anodize begins. Let the anodize proceed for one hour. Remove the part and rinse it in water to remove the acid. The anodize layer will give the part a milky appearance.

At this point, the part is ready to be colored, if this is desired. I use Caswell anodizing dyes, they have US and CDN websites and sell home hobbyist quantities. You can use clothing dye from Walmart, perhaps also try inkjet printer inks. Many water based dyes will work. Experiment on some test pieces. You can use sharpie markers as well. To do so, you must gently blot your workpiece dry with paper towels, as shapies won't write on wet aluminum anodize. See the main video and the dye video for more info.

Once colored, the anodize must be hardened and sealed. This is done by placing the part in a pot of boiling water on the stove, and simply letting the part boil for 15 to 20 minutes. You can get a sealer product from Caswell that you mix with the water, this reduces the boil time to a few minutes, and contains a wax that helps you buff the part once it is boiled.
Remove the part once it has boiled long enough, let it cool, and rag buff it to a nice shine. There is your first anodized laser part!

There are three videos I have included here. They are in HD and can be viewed full screen for best detail.

This first video is an overview of the whole process, showing black anodizing of a battery barrel and tailcap.



The second video looks at the dye step and sharpie markers



The third video is more detail on the electrical connection to the part.



The fourth video is about simple dye techniques.



Here is a photo of the results that you can get from a small anodizing setup that you can run in your garage or other well ventilated area.



You can refer to the info in this link to determine the suitability of various aluminum alloys for anodizing.

http://anodizing.co.nz/aluminium-alloy-anodising-anodizing

I hope that this info is useful to the community and that others will be able to use this easy and durable aluminum finishing technique.

WOW! It's that simple? This could come in handy for some future builds!

+1 rep fo sho!

Great tutorial, I learned a lot, and I love that last pic with all the different hosts, the first few look like lightsaber hilts +1

That's really neat I thought it was a lot more complex then that I will have to try this!

Do you have to polish the piece before you anodize it?

Wow thanks for sharing, really informative and great tutorial! +1 and :beer:

Thanks for making me even more busy. :na:

+1 for you!

Cheers! :beer:

jesus christ monkey balls. thats awesome! +1

Thanks for the tutorial. That will help a lot !
So anodizing and dying are two separate processes. What happens if you don't dye after the anodizing process. Does the milk color change in time or is the layer less strong if you don't boiled in water ( without dye)

Be aware that the part needs to be _really_ clean, otherwise you'll end up with inconsistent coatings, but it's a nice guide

Very nice Bill.. Thanks a lot. I'm definitely going to build my own rig sometime soon !! :beer:

Thats awesome.

How do you do fade, and marble effects like on the Krytons?

Thanks.

:thanks: for sharing your anodizing knowledge and detailed
informational videos. I've learned a few few more things
about small parts anodizing...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

Can you dye over the current Anodize that was dyed a different color.
e.g. Dying a anodized Black Matte to anodized Metallic.
Would that be effective or would it create a two tone effect which can be better or worse.

Best video and best subject I have seen all year !

Thanks for sharing your knowledge in this very useful art !

If I could rep you more I would, Thanks Great Job :gj:

@r1bro - The part does not need to be polished. You can go with matte, brushed, glass beaded, rough machined, whatever you want.

@blord - the dye is optional. For a clear anodize, just go straight to the boil pot after you rinse off the acid. The boil process will make the milky colored soft anodize go clear and hard.

@things - Excellent point, the cleaner the better. Any residue will prevent the spot it covers from anodizing. You can actually preserve a fingerprint in the anodize.

@hippyhop - In an upcoming video, I'll do some of these effects.

@livinglaser - Once the dye is in the anodize layer, it gets locked in by the boil process. I normally strip off the damaged or bad color anodize, and redo the part. You can't really go over it again like that.

Thanks to everyone who has commented. I was hoping that this would prove useful to someone. Hopefully we will see some results in the various build threads over time.

I will be adding videos to the series. One will be on problems in anodizing and their effects on the part. Another video will show different dye techniques.

Thanks a whole lot for this! I can't wait to see everybody's results!