Anodizing 101

by Jim Bowes

Based on the number of companies selling, and people looking for, anodizing services for their gun's aluminum bodies and parts, I wanted to provide this info to the paintballing community. I first came across the process in Super Chevy magazine, in an article about anodizing your own parts and brackets, for a custom touch on your hot rod. (* Original article by Bruce Hampson.) Often anodizing is considered and/or presented as a difficult and expensive procedure. As it turns out, it really isn't that hard or that pricey.

Supplies Needed:

The first thing to do is to get the following things together: First on the list is the most expensive item: a 6 to 12 volt battery charger. This item is what might make this too expensive for some paintballers. I (and most other hot rodders) already have one, for my car. If you don-t, then you will need to pick one up. They run from $45.00 to $110.00 depending on model, functions, etc. While it may seem like a lot, it does have other uses. (You could charge a battery, for example.) =) The next item, though not that expensive, will take some effort to find: battery electrolyte, a.k.a. sulfuric acid. This should be available at a battery wholesaler for about $2.00/gal. To make the negative ground, you will need some aluminum ground wire and aluminum-foil. The wire can be found at an electronics store for about $35/spool, and you should have the foil in the kitchen. If you happen to be out of foil, you can pick up some more at the store when you go to buy the last item for this project.

No super-special chemicals or solutions necessary to make the colors; just plain-old fabric dye. (Something like Rit dye, for about $5.00.) Rit offers something like 30-40 different colors, so you have quite a number of choices for what color you want your parts to be. An optional item is nitric acid: about $25.00/2.5 L. (This is used to clean parts prior to anodizing, but there are some cheaper alternatives. See end notes.) This is available at chemical supply stores. Should you not be able to find any, you can try to get on the good side of the high school science teacher. He may help you out since you only need a few ounces.

Safety Precautions:

There are a few precautions I want to go over to help keep you from blowing up the house or trashing the garage. First of all, do not mix or store your anodizing solution in a glass container. Something could happen to make it break, and most households are not equipped to deal with that kind of spill. You also don-t want to knock over the container, so a stable, rubber bucket makes a good choice. You will also need to be certain that the part you want to color will fit in the container without sticking out of the solution, and without touching the negative ground in the bottom of the container. Any acid that you don't use, keep in what it came in, or an old plastic bottle, like a bleach bottle. You can also store your used solution this way for doing more parts later. (Make sure that there is absolutely no bleach left in the bottle. Acid and bleach make chlorine gas. Very bad. Don't breath. Poisonous.) Safety also applies to the nitric acid, but in a different way. It is imperative that you label and keep track of this stuff, as it is a stronger acid than sulfuric, and more dangerous. The breakage/spill problem is not as likely since you won't have that much around. (Unless you bought more than a few ounces from the chem store.) The last note about the acids is to mix properly when adding acid and water. Always pour acid into water, never the other way, and do so slowly, being sure to mix in well. There is a reaction taking place and it releases a lot of energy. During the anodizing process, you will be running electricity through a weak acid solution. This creates hydrogen (just like charging a battery) which is very flammable. This stuff burns at the speed of thought when ignited, so do be careful. (Read as Remember the Hindenburg?) Make certain that there is some way to ventilate the project area, and DO NOT let any sources of ignition near the project area.Other precautions you should take include safety glasses, rubber gloves, and maybe some sort of drop sheet under the area.

Preparations:

One of the most essential things you need to do in order to get even color over the whole part is to be sure that the part is absolutely clean. You want it free of all contaminates, from dirt to the oils in your skin. This is where the nitric acid and some rubber gloves will help. A solution of 1-2 ounces of nitric acid in a gallon of distilled water will allow you to clean the surface in preparation for the anodizing. Aluminum oxidizes very quickly when exposed to air, so the easiest way to keep it clean is to clean it just before you are ready to start working on the piece. (You should rinse the part with distilled water before you put it in the next acid solution.) Other options are carburetor or brakes cleaners, or other similar degreasers. Soap and water will work also, or cleaners like Simple Green. These are cheaper, a nitric acid wash is the best. (You decide, it's your money.)

Make your negative ground with the aluminum wire and foil. Shape the end of the wire into a paddle shape and cover the round part with the foil. What you want to do is create a flat, round shape to sit on the bottom of the bucket, with a lead that comes up out of the bucket. You will clip the battery charger's negative lead to the wire that comes out of the bucket. When you are ready to start, you will want to mix up your immersion solution. In your rubber bucket, combine the sulfuric acid and water to come up with a solution that is about 30% water. (1 part water to 2 parts acid.) Place the paddle in the bucket and attach the negative lead. Then attach the positive lead to the part, making it an anode, and immerse it in the solution. (Remember that the two leads the paddle (cathode), and the part (anode) should not touch.) This is the best time to turn on the charger: once the part begins to fizz, leave it in there for about 10-15 minutes. After about this time the part should no longer conduct electricity. (You can also use an ohmmeter to check conductivity, but this is not needed.) Turn off and disconnect everything, and rinse the part in cold water. Don't use hot water! You'll find out why in the next section.

A couple of notes:

I have read some other procedures that say it is important that the copper lead from the charger does not enter the acid solution. The article says nothing about this, and shows a picture with the lead right in there. It may take some trial and error to find out if this is a problem. It wouldn't be a bad idea to get some scrap aluminum and play with it before you start anodizing your parts. You can check out the above, as well as pick the colors you like best. If you test out some colors, you'll also learn just how long or short you need to work with the color solution.

Color:

So now it doesn't conduct electricity, and is ready for color. It's been rinsed and waits eagerly to change to a new look. Don't wait too long to do the color, due to that oxidizing thing again. You want to mix up a strong solution of dye and water, in a container that can be heated. The solution needs to be at low heat, such as on the stove, so bread and cake pans work well. Again, you need something that will fit the whole part, but it's okay if it touches the bottom this time. I would recommend turning parts every few minutes just to make sure that you get all-over color. Inform your mom or wife that the pan can (and will be) washed out. It is important that the heat be low enough. If the solution gets too hot, you will seal the surface, and it will no longer take any color. (See, told you to rinse it in cold water!) Leave it in the dye until the part is slightly darker than you want it. The next step is to seal the surface of the metal in clean, boiling water. This will leech a bit of color from it, thus the slightly darker color in the previous step.

End Notes:

It is important to realize that the process described above will yield only one color on your part. At this time, I haven't found out how to do any of the splash type of anodizing. (That's okay though, it looks really ugly anyways.) Should anyone happen to figure it out, I suggest you submit it to Warpig so they can put it up for others who like it.

Also, this process is for aluminum. I don't know how, or if, it will work on other metals. (I doubt it.) Anodizing only works well on rock metal like bar or sheet stock, as opposed to castings. If it was forged or machined, it should have the density to take color through this process. I figure this shouldn't be too big a problem with the guns, but just thought I should let you know about it.

Something to consider when looking for a charger, is how many amperes it puts out. Without getting into any mumbo-jumbo, anodizing relies on 10 to 40 amperes per square foot. For small brackets and such, this is no problem. The larger parts in a gun however, may need the higher levels of amperes. The other note about part size, has to do with how long you leave it in the solution. Above it said 10-15 minutes, but that is for a smaller part. The larger parts may not only need higher amperes, but more time as well. I would recommend an ohmmeter, but again, I have one already.

So there you have it. Quick, fairly easy, and not too expensive. If you don't have the charger, then your first anodizing session could cost as much as sending your gun out to be done. But, then you can do it again for much less. Or do your buddies stuff. Or talk them into chipping in on a setup for all of you to use. We all know ways to help make things cheaper.

And the stupid statement required to cover myself... If you try this and something gets messed up, or someone gets hurt, you are on your own. Deal with it, you can't blame it on anyone else.

This is great! A lot of people talk about it being possible to anodize parts yourself, but no one seems to know how. Thanks a million for finally putting it in black and white. I'll bet there will be a lot of mad scientists out there trying this on their parts. There are so many parts that don't come in the right color, and the ones that are colored are usually blue, purple, or red. With the number of colors that Rit makes, and the fact that you can mix them to get custom colors (and you can always save the dye solution for later use with the same color - just remember the length of time that you left parts in before) this opens up a lot of new ideas!

I've heard that some folks have tried 'home brewed' anodizing before and the parts didn't come out as shiny as what you get off the shelf. Does this process make them look shiny like what you can buy at the store? Or were these folks possibly doing something wrong to get a dull finish?

I have been in the Anodizing industry here in Australia for over 12 years now, and what you say there will pretty much work fine... as to the quality of the product that will produce, its pretty hit and miss, Probably with the sealing process with the boiling water will be the downfall as just boiling water will not fill the pours that the anodizing creates that is why most Anodizers will use a solution that contains nickle. But give it a go people if you have the time and patience for it, i have my own little Anodizing plant in the shed and it works great, Nothing compared to the 17v 5000amp i use at work but it does work

This all sounds really great and easy. I have one question though. What about aluminum thats allready adonized, say with blue. How do you remove adonizing off of say a blue adonized heat sink that you want to make green? Or better yet, do you even have to remove it at all?

I haven't tried this myself, so I can't say it's 100% true (or foolproof), but I've read that you can us EZ-OFF oven cleaner to remove the anodizing from aluminum. The guy that was saying this, said that you'd need to coat it heavy, and let it sit over night. Maybe spray some more on there from time to time. In fact, if you have a thin or small part, you can spray the ez-off in a bowl or pan until it builds up deep enough for the part to be submerged. That way you don't have to come back and spray it again.

I have used ez-off to remove paint - works like a charm on metal or plastic. I also got some dye out of a set of HPI wheels that I picked up in a trade. They were dyed pink, so I soaked 'em overnight in the ez-off and by morning they were almost white. Then I re-dyed them a color that I wanted.

OK, I read this twice, but what is the base metal that is coating the aluminum?
It is a great artical but I thought the acid solution has to have a base metal disolved in it so that the electricity can plate the part!

The aluminum is being transferred from the aluminum foil to the part.

Oven cleaner will remover Anodizing providing the( "um" ) ( Microns) "thickness of the anodizing" isnt too thick, the higher the microns the longer it will take to remove, But most parts that i have bought for my cars that have been Anodized have very low microns and is quite easy to remove.

note that just using Sulphuric acid to Anodize without it containing high levels of Aluminium will take longer and give a poor result and uneven coating of the parts ....

Ideal acid level content 140-180 grams per ltr
Ideal Aluminium content in the acid 8- 15 grams per ltr

Awesome - actually verified by someone who knows what they're talking about. I gotta start playing 'Archie the chemist' in my garage now!!!

If anyone would like some extra details on this subject, i would be happy to help and you can email me at [email protected]

I just thought that people might want some simple and cheap instructions on how to anodize, and plus, uhh, what do you mean? The actual anodizing you cannot see, keep in mind the coloring process is done separate from the actual anodizing. So, if it is not a perfectly "even" anodizing, you will not see it. I just wanted anodizing for cool looks, not as much as making the aluminum harder.

I also have an anodizing shop. I see alot wrong with the instructions as listed. Number #1 you are not plating a part with anodizing but rather you are growing a coating on the part made from itself. Anodizing will not flake off like chrome "plating does. Number#2 the acid ratio is through the roof in the instructions at least for what I use. I run a ratio just the opposite to start with. Anyone that does this get a battery tester from the parts store and your mix should be at 1.100 on the gage. Next the text offers nothing about the temp to run the parts at. If you want to ruin some part do this with your tank a garage temp in the middle of summer!!!! The disolution rate ( rate at which the acid eats the new anodize as it forms) will be so high you will be lucky to build a layer to start with. The temp at which home brew anodizing works is between 65 and 70 degrees. Any lower and it slows the process down any higher and you are fighting disolution. Next ditch the foil. That will only cause big time trouble. A piece of aluminum sheet or lead works much better. Use the foil to wrap your leftovers. As for the Rit-Dye....it's junk for anything you really want to have pride in for any length of time. It's light fastness is bad and will fade pretty quick if you take your parts outside. There is anodizing quality dyes made for just this purpose that will not fade. As for sealing the part which "locks" the anodize pores Use boiling water but DO NOT put the part into the boiling water rather hang the part in the steam. You are looking at steaming it for about an hour. Placing the part into the boiling water will pull the color out of the part. i.e. you dyed the part red and with boiling water you will end up with a PINK part! I have a liquid sealer that is made to seal anodized parts that works real well. A battery charger will work just great ...but make sure it's a manual one and not an automatic one as an automatic one will be fooled by the anodizing process and will shut itself off. This is just the tip of the iceburg. I don't want to scare anyone off from trying but just remember that there is a number of chemicals needed to do a real top notch anodizing job. By the time you get the parts and chemicals together to do a handful of parts you would be better off just finding a shop to do them for you. Plus you don't have gallons of chemicals to get rid off. Just my 2 cents.

LAter,
Tim

Well, I'm glad I didn't start getting all the stuff to anodize with yet... Definitely not into pink!

You make some good points and by looking at your site it appears that you know what you're talking about. Would your company accept parts being shipped to you to be anodized? It looks like you offer about any color that someone can dream up. What affects the price? Are all colors the same price? Does the size matter? Quantity?

If someone sent you for example 6 small parts for an RC car (maybe a couple shock towers and four smaller parts), could you give us a rough idea on price range?

if you mix nitric acid and glycerine do you get notro glycerine ?.....

Make sure you dont do this with an air temp of below 40 degrees because you will get condensation on the surface and when you go to seal it you end up with little light colored dots.

My dad, knows a person that does anodising locally. A 5 min drive and a day later, I have anodised parts Also he does it for cheap because my dad takes alot of gyro parts to get anodised.

I prefer to get it done profesionally.

cool can i send my parts to you. [sm=wink.gif] come on, please?

For anyone wanting to de-anodize aluminum you can use any oven cleaner with lye in it(such as EZ off). But DO NOT leave it over night. It will form black pitted areas on the aluminum. Instead spray it on, watch it start to dissolve the anodizing(I will start as soon as you spray it on), and then start scrubbing it with an old toothbrush or thick cloth. And then wash it off with some water and you're done!