Just a thought and an idea.

Has any one done a home anodizing system.

Whats the idea?

ive seriously contemplated buying a home cadmium kit. zinc/cad plating would really be handy for all the small resto parts, fasteners etc that have become rusty over the years

I believe Eastwood still has plating kits

http://www.eastwoodco.com/

Caswell too: http://www.caswellplating.com/kits/index.html

Sparky! just wanted to give you a + to see you hit 100. I'm almost there also.....

Rit dye, battery charger and battery acid are all you need to anodize aluminum at home.

Back atcha Dodgerunner, thanks!

I've got plenty of swimming pool acid. I think it's muriatic (hydrochloric). Will that work or does it have to be sulfuric? They sell both kinds at the pool supply places.

edit: I want to anodize a putter that has a (previously painted) aluminum head.

[This message has been edited by spark1 (edited 02-18-2007).]

It has to be sulfuric.

Put some aluminum foil in hydrochloric and find out why.

Ryan,
What do you have to do to anodize at home?

quote Originally posted by midengineracer: Ryan, What do you have to do to anodize at home?

Some good links:

http://www.wcc.net/~jkmccoy/shop/anodiz.htm

http://www.focuser.com/atm/anodize/anodize99.html

Saved this info,about a year ago,for anyone whos interested (I haven't tried it yet).
Anodizing
In the 1920's, aluminum found mass production and began to be widely used. It was durable, ductile, and most of all very light weight. Anodizing was invented thereafter to help it become even more durable. It also gave a means for adding color to the aluminum surface itself which was much more durable than paint because the anodize film was part of the aluminum itself. There are many kinds of anodizing to choose from and each of them has distinct advantages as well as disadvantages when compared with the other anodizing processes. In my opinion, decorative anodizing is the easiest type of anodizing to learn, gives the best appearance, and produces the very hard surface suitable for 99% of the aluminum applications out there.What is the purpose of Anodizeing?Increased strength,Abrasion resistance,and corrosion resistance,while adding a beautiful finish to aluminum's comparitive low cost,light weight and malleability.Anodizing is a very simple process involving the use of little more
than some diluted battery acid and a 12V charger (although it doesn't
work on all aluminum alloys).Just
remember that any tiny spec of contamination (oil, dirt, even a
fingerprint) will show up. Doing color is as easy as doing clear; just add dye to the water. I
use plain old liquid Rit dye in the boiling water bath and it works
just fine. I have pieces done in black over a year ago that look
every bit as good as the commercial dye. I've also done red and
green, and they look great also. I mix the solution to about double
that recommended on the bottle of dye.
On reading my reply, I realized that 'mixing to double' is a poor
description. I mix the dye using half the water specified. There,
that should make sense.Rit dye does work, although you can get inconsistent results. I used if at
first, but one batch came out with a green cast to it. Some speculation
put the cause at pore size in the anodize layer selectively taking up dye
particles. Probably only an issue with black.

I switched to Caswell black dye and have never had any problems like that
since.I also had a problem with Rit. Part came out splotchy and
greenish/yellowish ick, but still corrosion-free after a year outside
I just use those disposable nitrile gloves you can buy in packs of 12
or more. Since you're working with an acid, it's not a good idea to use your
bare hands anyway.

Dyeing is a very simple addition to the basic process and I've had
great success using regular fabric dyes to get impressive gold and
red colorations that have yet to fade even when the parts anodized
are operated at high temperatures for prolonged periods.
The accepted way of dyeing is to take the work from the anodizing
tank, rinse in cold distilled water, imerse in the dye bath for several
minutes (with gentle agitation) then remove and seal in steam or
boiling water.

That's the system I use and it works great. I would be worried that
putting the dye into the boiling water sealing bath might cause the
pores of the anodized layer to be closed before the full dye-uptake
has been achieved.

I know that when I take the work from the dye bath I steam it for a
couple of minutes and then, when I put it into the boiling water, there
is very little leaching of dye from the work. Whether this is because
the steam has already sealed the work or whether the boiling water
causes a very rapid sealing I don't know.
I use Dylon brand -- they come in little plastic pottles about an inch
in diameter with an aluminum tear-off lid and are available in hot or
cold water versions. I've used both.I annodize in the acid bath for 120 minutes, keeping the bath at 68-70F with ice cubes in a water jacket (a bigger tub). I always use the liquid Rit, and mix it using half the specified amount of water for a really concentrated solution. I then heat the solution on the stove and submerge the work into the solution when the temperature is about 90F. I then raise the dye bath temp and hold it at 130-140F for 30 minutes. I then raise the temp until it just starts to simmer, then pull the piece and rinse it in a boiling water bath for a few seconds, then steam it in a vegatable steamer for 30 minutes.

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 Anodizers. 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.
(Editor's Note: While Mr. Bowes recommends not using a glass container, we highly recommend use of glass within a plastic container to help keep the acid from eating through plastic, but keeping the glass less breakable in the event the container falls over.)
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. DonÀ Àt use hot water! YouÀ Àll 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 paintgunÀ Às parts. You can check out the above, as well as pick the colors you like best. If you test out some colors, youÀ Àll 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.
The theory of Brush plating is simple
The rectifier supplies a negative charge to the work piece and a positive charge to a hand held wand which has the anode attached to the end of it. The anode is covered with an absorbent material which holds the plating solution. The anode can either be dipped in the solution or in some large jobs the solution is constantly pumped up to the area being plated. The anode is then applied to the work piece by the operator, or the work piece can be moved under the anode, such as a moving shaft. The movement will apply even plating on the entire area being plated. Plating occurs only where the anode contacts the work piece.
In a tank plating
We must have a tank of sufficient size to hold the work piece with room for the anodes and at least 3 to 4 inches of space on each side. Jewelry and small car parts are a good example of items that take well to tank plating, and the tanks can be as small as one quart size in some cases. In electroforming which is the plating of non-conductive items, a tank system must be used first to apply the copper over the conductive paint. A tank has the advantage of being able to build-up thicker plating without you being there or doing any labor during this step. With most solutions the anodes must be equal to or greater than the work piece. If we use anodes of the same metal as the solution then basically the solution goes on but the anodes dissolve and must be replaced. When using stainless steel anodes the metal is used out of the solution but the anodes don’t wear out. The solution is then replaced.
Advantages of tank plating
Easier plating of complex shapes. In most cases multiple parts can be plated at one time. In electroforming the copper must be tank plated over the conductive coating. In some of the tank solutions the brighteners, which are chemical additives can save you some of the time and labor of polishing. The pieces plate out bright.
Differences in the two types of plating
The plating chemicals used in brush plating are much more concentrated than the solutions for tank plating, therefore they are not interchangeable. In most cases there are approximately 15 times more metal in them. It does make them more expensive per ounce but they also cover much more area than tank solutions. The nice part is that you don’t have to buy such large quantities of solution to do the job. Also because of their concentration the brush solutions can build-up thickness faster than tank solutions.


E-Polishing
Electrical polishing is a method of polishing various metals such as stainless steel, aluminum, steel, and copper via an electrochemical process. You simply submerse a clean part into one of our electrical polishing chemicals, turn on the current via a power supply, and in a minute or two, you'll will have a nicely polished part. The electrical polishing tank is set up the same way as a plating tank. You'll need a tank, electrical polishing anodes, a power supply/or battery, a tank heater (or aquarium heater), and that is it.
Do not jump the gun here. Electrical polishing does have its limitation. You cannot put a part in the solution that is rusty and pitted then expect it to come out mirror-like. The part has to be in reasonably good shape or has to be sanded smooth. The parts have to be rust-free and dirt-free. Stainless steel will electrical polish out to a mirror-like finish just about every time. Aluminum shows good results but 6000 series aluminum alloy seems to come out the best. Steel and copper also do fairly well, providing it is reasonably pure.
Electrical polishing as a business opportunity is very good, in this writer's opinion. It is easy to learn. The learning curve is only about one to two weeks. The market for it is very good, especially for stainless steel. There is a whole lot of work to be procured in the medical as well as the food industry. Medical equipment are made of mostly stainless steel and are very expensive. To save money, clinics and hospitals would rather refurbish their stainless steel equipment rather than buy new ones. The electrical polishing procedure will actually sharpen surgical tools as it polishes it.....neat, huh? As for the food industry, the FDA requires that ALL metallic equipment that comes into contact with food be stainless steel. And by law, these items has to be electrically polished periodically. Pick up your local phone book and you'll only find little if any companies that do electrical polishing locally. So chances are, these local medical clinics and restaurants are sending their stuff out of town or even out of state. So being the local guy that offers this same service, chances are you'll get their business. The process is quick so you can get quite a few loads in and out each hour. At my shop, I deal with only medical equipment and right now only have a 75 gallon tank. Just to give you an example, I get $7-$8 a piece for scalpels. That doesn't sound like much but I get a few thousand of them at a time. I do 10 pieces on my rack on each run and I get about 5-6 runs an hour. Do the math and you'll will see that I can make anywhere from $350 an hour and up. Not bad money for a line that only needs one person to run it. Even with, say, a 20 gallon line, you are still looking at at least $100 dollars an hour. With electrical polishing professionally, you will need very little equipment compared to other plating process and EPA regulations are very light on this process.
ANODIZING STEPS:
USE A WATER BASED DEGREASER OR ULTRASONIC CLEANER on any part that has been buffed with a buffing compound. This will ensure removal of all compound residue. DO NOT use solvent such as acetone, thinner, or etc. on aluminum. The metal is very porous by nature and tends to absorb the solvent into its pores and leaches out during the anodizing or dyeing process which will ruin the final finish.
RINSE
ALUMINUM SOAK CLEANER (soak at 110-160 degree F for up to 20 minutes)
RINSE
ETCH for 20 seconds to a few minutes. Once you see the aluminum fizzing, count to 10 and pull the part out. Etching gives aluminum itself more receptive to plating or anodizing. Or if you are looking for show anodizing finish on polished aluminum, BRIGHT DIP may be considered in place of Etch. When using our new formula Bright Dip, use it here in place of HP Etch. Bright Dip should be desmutted prior to anodizing.
RINSE
DESMUT-LITE for 1-10 minutes depending on alloy (Do not confuse this step with a De-Oxidizer. A De-Ox will only remove smut from the Etch. Our Desmut-Lite serves three purposes in one. Like a De-Ox, it serves to remove the smut that may have formed from the etching. It smoothes out the aluminum which a De-Ox does not. Thirdly and most importantly, it will eat up alloy materials such as silicone, copper, magnesium, etc from the surface of the aluminum and leave the surface as almost purely aluminum. Again, a De-Ox will not do this either.
RINSE
RINSE IN BAKING SODA (0.3-0.3 LBS PER GALLON) AND WATER
RINSE
ANODIZE (Hard Coat, Decorative, Marine, or ST)
RINSE IN BAKING SODA (0.3-0.3 LBS PER GALLON) AND WATER
RINSE
DYE for 15 seconds to 10 minutes depending on color depth you want to achieve
RINSE
RINSE (or MASK AND STRIP DYE FOR MULTICOLOR ANODIZING LOOK AND GO BACK TO STEP XV)
ROOM TEMP SEALER (you can use boiling water or steam for 45-60 minutes or Room Temp Sealer for 1-5 mins)
RINSE.


http://www.eng-tips.com/gpv.../367/lev2/15/lev3/55
http://www.focuser.com/atm/anodize/anodize99.html
http://www.anodizing.org/
http://www.hobbyplating.com
http://www.mini-lathe.com/A...odizing_aluminum.htm
Internet Search words are: Tank Plateing,Anodizing,Anodizing Kits,Brush Plating,E-Polishing,Decorative anodizing,Anodizing Rectifiers,Marine Anodizing Kits,Titanium Chiller Coil,Plating,Electroplating,Selective plateing,Electrocleaning,Metal-Plating-Chemicals,Gold Alkaline (Pure Gold),Silver (cyanide),Zinc Alkaline,Copper Alkaline,Platinum Alkaline

[This message has been edited by James Bond 007 (edited 02-19-2007).]

gezzz!
Can you use a more rude color for the eyes???? maybe hot pink or yellow??:roleyes:

jamesbond007: Please change your color contrast...very harsh on the eyes.

Anodizing Aluminum
(pieced together from various sources, including the newsgroup. JK)

First, this is only meant to apply to aluminum. Other metals, such as titanium, niobium, and possibly magnesium and others, can also be anodized (see for example http://members.aol.com/t2945/page1.html.

Aluminum oxidizes very quickly, and rapidly forms an aluminum oxide coating that inhibits further oxidization. This coating is useless as is, in terms of protecting the metal, because it is so thin. A thicker coating can be produced by immersing the part in an electrolytic solution and passing an electrical current through it, similar to electroplating. The resulting film is nearly colorless, and can be easily dyed because it is very porous at the molecular level. Then, by placing the part in boiling water, the film's pores can be sealed; the oxide changes from one form to another as a result.

To be more specific, parts should be very clean and grease-free. Commercial plants will first clean and etch the surface in a caustic solution, such as lye (sodium hydroxide), followed by a thorough wash. The parts are placed in an acid solution, such as 15-25% sulphuric acid, and connected to the positive source of a power supply (use only aluminum hardware to make the connection; no copper in the solution!). The part(s) comprise the anode, and the cathode is lead (lead sheet, or the whole tank might be lead). Appropriate current is applied, e.g. 1.5 amps per decimeter (3.4 square inches). This lasts 15-25 minutes if no dying is planned, or 45-60 minutes for dying.

Dying is the next step, if desired. Since the pores are extremely small, many common dyes will not work. Some wool dyes are known to work, or you can purchase commercial anodizing dyes from an industrial supplier. Typically this involves immersion in the dye solution, which may have to be heated to be effective. (Steve Rayner reports that telescope builders like a black anodizing dye called Nigrosin Biological Stain, which is water soluble and mixed 1 teaspoon full to a quart of water; his bottle is labeled Aldrich 19,828-5 and cost around $35.00 Canadian, for 25 grams).

Sealing is then done by putting the part in boiling water, which changes the film from gamma aluminum oxide a hydrated form called boehmite. Boil for about 20 minutes.

Another anodizing process involves using chromic acid. This is not suitable for alloys with more than 5% copper. The film is thinner, but very durable. The very thin film is also a benefit when very close tolerances must be maintained. However, because chromic acid is a very nasty chemical, its use on an amateur basis is discouraged, and its commercial use may be closely regulated.

Anodizing is sensitive to the type of alloy. For example, alloys for die casting have a lot of silicon, which makes it pour and mold well, but it makes anodizing almost impossible.

By all means, find a few references and read them carefully before attempting anodization. If at all possible, try it out on scrap pieces before attempting it on your masterpiece. Be sure to flush the part completely to remove remaining acid.

An alternative is to use a commercial firm to do the anodizing. Some net folks report they can be a bit rough to deal with, as they may be more used to dealing with large jobs and may not appreciate a home machinist with a single 5-inch part. Look in the phone book under anodizing, plating, or electroplating.

Some have reported using a lye solution to treat the surface, which yields a fairly uniform fuzzy surface, that may be acceptable as a final surface without further treatment. Don't use a strong solution or the aluminum will disappear too fast; do this in a well ventilated area, as hydrogen gas is emitted, stay away from flames/sparks, and remember that lye will eat people as well as aluminum! The resulting surface can be dyed, or painted with a chromate primer. (One tablespoon of lye per pint of water has been suggested).

Another alternative is a product called Aluminum Black from Birchwood Casey, which is often advertised in model railroading magazines, and may also be available via gun stores (it is in the Brownells catalog). Brownells also lists a nickel plating solution for aluminum, though it appears non-trivial to use.

See also the ArtMetal WWW pages at http://wuarchive.wustl.edu/.../metal/ArtMetal.html for information on anodizing for artists (more specifically, http://wuarchive.wustl.edu/...nishes/anodize.html)

See also http://easyweb.easynet.co.uk/~chrish/t-anodis.htm

Howard Jones posted an item showing how to anodize at home, based on a handout of Graeme Ockleshaw..

References:


Aluminum (Volume 3): Fabrication and Finishing Kent Van Horn, Editor American Society for Metals, 1967 Library of Congress #66-16222 813 pages
Electroplating for the Amateur, by L. Warburton. Model & Allied Publications. Available via Argus.
The Surface Treatment and Finishing of Aluminum and its Alloys, Edited by S. Wernick, R. Pinner, and P.G. Sheasby. Published 1987 by ASM International, Metals Park, Ohio. 2 volumes.
ARTISTS ANODIZING ALUMINUM- the sulphuric acid process, by David LaPlantz. ISBN: 0-942002-03-2, apparently published by Press de LaPlantz Inc. Box 220 Bayside, CA USA 95524; It's about $20 US. There is also a book and tape for aboout $45. Both should be available from Rio Grande Supply (see vendor section). The book is extremely thorough and contains several methods of anodizing with lots of pictures and references. It is intended for small individual pieces, at home in the garage or basement.
Metal Finishing - Guidebook and Directory. Metals and Plastics Publications, Inc. One University Plaza, Hackensack, NJ 07601
Anodizing Aluminum, by Harold Hoffman. Available from H & H Publihing, 7174 Hoffman Road, San Angelo, Texas, USA 76905, or Centaur Forge. This book seems fairly complete, with supplier sources.
Anodizing Aluminum in the Amateur Workshop, Ham Radio Magazine, January 1979, pages 62-69, by David W. Hembling. Sadly, this magazine is out of business, but should be in larger libraries, or available via inter-library loan. This article lists several other references, including addresses for dye makers.
Passivating Aluminum Alloys, in 73 Magazine, September 1965, pages 74-80, by Robert A. Kidder.
Reynolds Aluminum, years ago, published "Finishes For Aluminum", now available as a reprint from Lindsay Publications, P.O. Box 12 Bradley, Il 60915-0012 (Don't call, write). It covers many different finishes including anodizing.
Some jewelry-making suppliers deal with anodizing.
The magazines Strictly IC and Model Engineer allegedly have discussed this, but I don't have exact references.
Argus Workshop Practice Series, number 11, by J Poyner.
Sandoz Chemicals Corp (now apparently Clarion Corp) supplies dyes for aluminum anodizing. Their phone number is (704) 331-7000.
Kepro in Fenton, MO sells black aluminum anodizing dye for their aluminum anodized nameplate kit. They sell it in small quantities. The phone number is (800) 325-3878 or (314) 343-1630.
How to Anodize Aluminum, Popular Science February 1963, pages 144-146.


--------------------------------------------------------------------------------

ADDENDUM: On May 16, 1996, Patrick M. Riggs (pmr0811@tamu.edu) posted this nice description of how *he* anodizes aluminum, and copper as well. JK

A long time ago, I came to this newsgroup asking for answers on how to anodize aluminum, and nobody really had advice. Since then, of course, I've seen lots of suggestions. In any case, at that point I promised to post if I had any results, and never posted except to mention my success. Well, while there are probably better methods out there, this is what worked for me, and has continued to work for me. I hope this is helpful. BTW, it has been a while, and Sandoz chemical is now called Clarion corp. Their proprietary anodal ms-1 is basically a weak nickel acetate solution. As to where to get sulphuric acid, I wouldn't know, since I work at a university where such things are readily available.

I hope this helps, and thanks to those who gave me advice along the way.

Oh yeah, and be careful . . . sulphuric acid is dangerous (I have "bad lab practice" reminders in more than one pair of shorts -- not that I recommend wearing shorts in the lab . . .) and eats an awful lot of otherwise sturdy materials. Also, beware of the high currents. I, of course, take no responsibility for anything (and that seems to be my problem in general).

Hard anodizing:

Sulfuric acid at 13% by volume, at a temperature of 3 degrees C. Note that the temperature is not overly important, so long as it is close. The current density should be ~15 amps/square foot. The aluminum piece should stay in the bath for at least 2 hours, with four hours being optimum.

As an alternative to hard anodization, leave all conditions the same except for the temperature, which should be 70-75 degrees C. The difference in the two procedures is the thickness and quality of the anodic layer. Hard anodization leave the material more absorptive.

The cathode, or negative lead, should be lead, with the anode to catho proportion being about 1:1.

For dyeing the object, there are two options:

Rit dye:

Rit is a standard wool dye, which can be purchased at any grocery store. This method is both inexpensive and offers a wide variety of colors. The drawbacks are that Rit, an organic dye, is not light fast, and will fade in direct sunlight.

With Rit, simply prepare a bath of about 50ml/litre at about 70 degrees celsius. One hour minimum is required, with the preferable duration matching the anodization time.

Black MLW:

Black MLW can be purchased from Sandoz Chemical (my contact was Ron Rupple (214) 423-1674, the sales rep for texas. The company is based at (704) 331-7000.) The price is between $15/lb and $60/lb (don't have an exact quote, but this is the range of prices for all of their black dyes). Small test quantities can be obtained.

Black MLW is favorable because it is a) light fast in the visible (being inorganic), and b) a rather flat black. It's drawbacks are expense (a minimum order is 5 lbs, which is an awful lot of dye), and requires special working procedures (the dust is hazardous to the lungs).

Black MLW is, however, simpler, and more convenient, to use. The temperature should be between 51 and 60 degrees C. The duration being 5-10 minutes depending on quality of blackness desired. The concentration (keep this in mind before ordering 5+ pounds) is 10 grams/litre.

Sealing:

The sealing process hydrates the porous anodic layer, closing it, protecting it, and sealing in the dye. For most applications, sealing is desirable.

Supposedly, this process can be done with boiling water, but I've only managed the following.

1) Simply leave the piece in the dye bath, and boil the dye bath for one hour. This will require removal of the excess dye afterwards and is not generally recommended.

2) 2% anodal MS-1 (again from sandoz chemical (though, nickel acetate should work as a substitute). The temperature of the bath should be between 70 and 87 degrees C, with a duration of 5-20 minutes (depending on porosity and thickness of coating . . . longer never hurts).

Note that after each step, the object should be rinsed with deionized water to avoid contamination. I did this all with distilled water, though deionized water should still work.

Important information about the piece. The purity of the aluminum is important. The higher the silicon content, the less likely the process is too work. Also, the product should be newly machined (for a shinier, more professional finish) or sandblasted (for a flatter, though less even, finish). All oil, dirt, glass beads, etc, must be removed prior to the anodization process. This can be done by thorough cleaning with acetone and methonal (soap is dangerous, since phosphates in the solution tend to negate the anodization process). For better cleaning, immerse the part in 1 tsp/200 litres NaOH (be careful). For small parts this is undesirable, since the NaOH actually removes aluminum. After this bath, a smutty brown finish is obtained. To remove, rinse the part, and soak in a 10% nitric acid solution until a satin finish is obtained.

Copper anodization:

While aluminum anodization is typically clear (depending on the alloy and the process used (there are various other processes using different acids, the most common being chromic and oxalic), copper, at least via this process, anodizes black.

The desired voltage is 6 volts across the circuit. The bath should be 120 grams/ litre of NaOH. The temperature MUST be between 82 and 99 degrees C or the process will not even begin. The duration of the anodization process is 30 seconds to 3 minutes, depending again on the quality of black desired . . . more time, flatter black. The cathode is Steel in a 1:1 ratio. Again the piece must be dirt/ grease free.

This process will also work for brass, though it is shinier. Also, different colors may appear under the black, depending on the brass.

For both of these metals, remember that they oxidize quickly in air (which is not the same as the anodized layer . . . though in aluminum, this layer is also protective). Therefore, they should be anodized as soon as possible after machining and preparing.
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ADDENDUM: on August 12, 1995, Jerry Kimberlin (kimberln@crl.com) posted the following on blackening aluminum. In this case it is not an anodizing finish, but this seemed to best place to stick the information! JK

There have been several postings about blackening aluminum recently. I wrote an article for *Live Steam* magazine back about 1977 on the subject and have modified it a little since then. I do use it myself and thought that it would be of interest to the newsgroup. So: BLACKENING ALUMINUM by JEROME KIMBERLIN There are several ways to color aluminum black and among them are black anodizing and paint. You could rub dirt into the aluminum surface, I suppose, but of all the methods, I think chemical coloring is the superior method. It is certainly cheaper, faster, and home use allows the model engineer greater flexibility in the timing of his decoration of models in progress.

Surface preparation of parts to be colored black is all important as any irregularities are not covered by this finish. Paint does build up and fill in scratches and other voids. Castings, however, should look like castings if the prototype used castings, so surface finish is always adjustable to the builders idea. The point here is to emphasize that this blackening technique will not cover up mistakes.

You will need three chemicals. These are: Nitric Acid, Copper Nitrate, and Potassium Permanganate. You will also need some good quality water - either distilled or deionized. I will give the dimensions of the mixture in both metric and English units so that both types of measures are accommodated:


Take: water 3 quarts 750ml
Add Acid 1/2 oz 5ml
Add Copper 3 oz 25gm
Add Permanganate 1 oz 10gm
Add Water to make 1 gal 1 liter

Obviously you will have to make up more or less solution to fill the container you will use to color aluminum parts and the parts to be colored should be completely covered by the solution. You should use a glass or plastic container. A metal container will poison the solution prematurely.

At 75 degrees F (24 C) temperature, the blackening process will take about 15 minutes using a fresh solution. If it takes longer it means the solution is deficient in one of the components. Usually, copper nitrate and nitric acid need be added.

Aluminum is a strange metal to most of us. While we cannot see it, the surface of a newly machined or cleaned piece of aluminum combines with oxygen in the air to form a self protecting coating of aluminum oxide. This happens within minutes. If this surface continues to grow (get thicker) the blackening solution described here will not work satisfactorily. Thus, the piece to be colored should be cleaned just before immersing into the coloring solution. In my experience, glass bead blasting is a superior way to clean the aluminum surface and the choice of bead size determines surface finish. Once the bead blasting has been accomplished, the beads can be washed off with hot water and the aluminum piece immersed in the blackening solution. I recommend that the time between blasting (cleaning) and immersion in the blackening solution be less than two hours. I once waited five hours and was disappointed in the results. Once the blackening process has been completed, wash off the workpiece with tap water, drain and spray with WD-40 or other water displacing oil.

There are a number of ways to clean aluminum satisfactorily. It is possible to simply sand the surface clean, or scrub it clean with an abrasive. One can also chem clean aluminum by degreasing the workpiece then dipping it into lye (Draino, for instance) for a few minutes or seconds as required, then rinsing. The shape of the workpiece and the model engineer's facilities often dictate what method of surface preparation will be used.

Model engineers wishing to use this solution to blacken aluminum castings or other parts should be aware that the chemical components may be hazardous. While the solution itself is not particularly dangerous it can make your hands purple, so use rubber or plastic gloves. Potassium Permanganate is classified as an oxidizer even though dilute solutions of it are used throughout the world to sterilize vegetables used in salads, etc. Concentrated nitric acid is just plain bad. The technique for using it is to pour out a little in a glass container and then use an eye dropper to transfer the liquid to a measuring container when the volume wanted is small, such as that described here. Nitric acid also turns your hands yellow, hurts, and removes fingerprints. A good way to avoid eye damage is to wear a face shield such as the one you should be wearing when working in front of your grinder.
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ADDENDUM: On July 4 1997, Dave Sage (dsave@inforamp.net) posted a lengthy description of how he anodizes at home --

I have received a few requests to explain the process of anodizing at home. I have had very good success so I'll pass the method I use along for others. I'll leave the source of supply of chemicals and materials up to you because I did a lot of searching and then begged most of them and even I will be in trouble getting more when I run out of them.

The fine print:

Of course I assume no responsibility for anyone's safety in following this procedure.

The first thing to do is go the local hardware supplier and get a cheap range hood ($35) they have a nice light too - nice to see what your doing. I mounted mine on a bench mounted stand and put a piece of flexible dryer vent hose on it to point it out the basement window. The fumes are pretty nasty - probably sulfuric acid vapor - and even a little of it will cause coughing and lung irritation for some time. There isn't much given off and with the vent there is no problem and no sign of any smells outside the hood area. I also use a respirator if I need to get my head in close for a view of the process or I hold my breath.

I intend(ed) to improve on the equipment used but since it worked so well with the quick prototype setup I have, I left well enough alone for now.

I purchased a Rubbermaid plastic contained about 18" long about 10" wide and about 8" deep. I then went to my scrap metal dealer and got some sheet lead about 1/16 thick and cut it into long strips. One strip goes over the edge at the long end of the container, down inside, across the bottom and back up and over the edge on the other end. This bit over the edge helps to hold the lead in the container and it's handy for clipping the power connection to (large battery clips). There is a second strip making a (flat) ring around the inside of the container below the proposed liquid line. The ring and the strip are soldered together at both ends for electrical continuity. I used a big 150 watt iron used for stained glass work for that operation and any regular solder. Don't use regular fasteners. Everything must be aluminum or lead (so they tell me).

I will add that I have no idea if all of this lead is necessary. A single plate at one end may be all that is necessary. I just thought it a good idea that current can flow from all directions to the part which will be hanging in the bath to avoid "shadows". I have also heard that aluminum is also acceptable as a cathode. Aluminum may be easier to work with, the lead is very heavy and floppy and you have to be careful when you turn the contained over or the lead tends to sag. Anyway that's what I have and I'm sticking with it.

I just happen to know someone in the plating business, so obtaining sulfuric acid was no problem. I also think you can get it from Auto supply houses - they may have it around for putting into car batteries.

NEVER ADD WATER TO ACID

ADD ACID TO WATER

ALWAYS USE THE PROPER SAFETY EQUIPMENT, ETC. ETC.

ALWAYS STORE ACID IN AN APPROVED CONTAINER.

Wear old clothes - no matter how careful you think you've been you will find a few holes in you pants after you do the next laundry.

Make a solution of acid that has a specific gravity of 1100. You can use a regular car battery hydrometer to measure this. It's not too critical. This would be approx. the concentration in a discharged battery. I don't recommend using old car battery acid as it probably has other chemical in it that may mess up the anodizing. Make enough of this to fill the Rubbermaid container to a safe level.

So far I'm just using a regular 12 volt car battery charger as a power supply. Although the one I'm using is one of these automatic jobbies that shuts off when the battery is charged, I don't recommend this type because it tends to be fooled by the anodizing setup and shuts off, or quickly clicks on and off and is generally a pain in the butt. Just use a regular type charger - maybe one that has a 3amp and 10amp range.

For good measure I put a very large capacitor of about 20,000 micro farads across the output - this obtained from a local electronics surplus house. Just make sure the cap is rated for at least 25 volts. I'm not sure this is necessary and I had good success without it too but I do know that battery chargers are not a filtered supply and I just thought getting rid of the ripple might make things better.

The negative lead of the supply and capacitor goes directly to a clip connected to the lead liner in the container.

In series with the positive lead I put a 25 watt rheostat of about 2 ohms to control the current. Some people say a piece of resistance wire can be used here. I had the rheostat - so I used it. The system works without it but I found that if the current to the parts in the container gets over more than a couple of amps I was having trouble with the electrical connection going bad and the connecting leads were anodizing and the part wasn't. Since the battery charger isn't variable the resistor was necessary. It does get very hot though so be careful.

An anodized surface is non conductive and if the connection goes bad between the part and the wire used to suspend it then the wire anodizes and insulates itself from the part. This is the single biggest problem I have with my set up.

As I mentioned the parts to be anodized must be suspended in the acid solution so as not to touch the lead at the sides of the container. I just used a simple wood stick across the length of the container with a few screws spaced along its length to wind the wire to and to give a point to clip the positive power lead.

The more polished the piece is BEFORE you anodize it the nicer it looks after. I usually shine the pieces up until I can see my face in them. Anodizing will not cover any sins.

THE WIRE USED TO SUSPEND THE PARTS MUST BE ALUMINUM. I understand copper or steel will contaminate the solution and the part to be anodized. For this I purchased a roll of regular aluminum wire feed welding machine wire available at any welding supply or home depot. It seems to work, I couldn't find anything else although it may be the source of some of my connection problems. It is of a very hard alloy of aluminum and would rather break than form to the part. But I use it anyway.

Use a good long length of the wire and wrap it very tightly through any available holes in the part. Be aware that at the point the wire touches you won't get any anodizing - hence no color if you dye it, so don't wrap the wire around the part proper. Double up the wire and twist it tight with pliers. Like I said before this electrical connection is my biggest problem. If anyone has any way to improve this situation let me know.

You should wear rubber gloves from now on as you should not touch the part else you get a greasy spot that won't anodize well.

First you must clean, clean, clean the parts to be anodized. I use laundry soap because it cuts grease and is a bit abrasive. I then put the piece in a plastic container and with a brush, use a bit of caustic cleaner (again obtained from my plating shop friend). I think a very mild lye or caustic soda solution would work here. The parts tend to bubble a bit with white foam, but it DOES NOT etch the surface and I don't leave it on more than a few seconds. This step may not be necessary if you scrub the part well with soap and water. The purpose is to be sure there is no oil on the part. Rinse the parts thoroughly. I then like to leave them submerged in water because they dry in the air and sometimes look a bit white - something that LOOKS like it may affect the anodizing.

The parts are then suspended from the wood stick and screw by the wire in the acid so as to be completely covered but not touching the sides of the container.

Connect the positive of the supply - from the rheostat and capacitor - to the screw and wire holding the part(s).

I'll assume one part is being anodized here because the description is easier.

Do some calculation of total surface area in square FEET of the part - DON'T FORGET ALL SURFACES - inside and out, edges etc.

Turn on the power and measure the current. I usually find it to be around 3 amps or so. If it goes way high change the rheostat setting or select a lower output from the battery charger. Like I said before the electrical connections from the wire to the part are the biggest problem and I find that if the current gets much over 3 amps the connection fails and the wire - not the part- anodizes - actually it corrodes away to nothing and the part falls off. The part should soon begin to have small bubbles all over. If not, and the wire does, you have a bad connection. I usually have the least problem with leaving the current to each part at about 2-3 amps. It takes quite a bit longer to get the job done but with less headaches. Jiggle the part occasionally so you don't have gas bubbles lingering and shielding the parts from the acid solution.

The rule of thumb I have been using is to apply 900 amp/minutes per square foot of area. Sounds like a lot but for a 1.5 inch diameter by 4 inch long piece of bar (I hope I get this right)

3.14 x 1.5 x 4 = 18.8 square inches for the sides plus 3.14 x .75^2 = 1.8 square inches for the ends. equals = 20.6 square inches total area There are 144 square inches in a square foot so... 20.6/144 = .143 square feet of surface

The part is drawing 3 amps so 900/3 = 300 amp minutes per square foot required.

300 x .143 = 42.9 minutes. (sounds about right)

This is only a rough guide. In reality I start with this and then watch the part. If the part was nice and shiny when it started you can watch the part as it anodizes and I have found that the part turns ever so slightly a milky lemony yellow color. Definitely not as bright and shiny as it started. This would be the aluminum oxide layer buildup. If I hadn't told you this you might not notice, its very slight. But I have found that if my time estimates are approaching and the part looks this way it always seems to work out well and takes the dye nicely. Not scientific but seems to work.

After the anodizing bath I immediately put the parts in a bucket of water or they can stay in the acid with the power off - but don't let them dry. I just like to use the same fume hood while I do the dyeing so I have to remove the acid container and empty it out etc. Keep em wet.

Sorry, I won't recommend a source for the dyes but I got mine as samples from a dye supplier. Again I found this guy through my plating friend, although I found a lead on my own by calling chemical companies and asking for their reps. You can try your local anodizer but for some reason they guard their suppliers - maybe because they know the procedure is simple and they don't want you to take business away by doing it yourself. Sandoz chemicals makes a black dye, maybe they can put you on to your local rep and you can go from there. I don't want everybody bugging my supplier for samples - you'll mess up my credit for more :-)

An interesting story - before I had the bright idea for aluminum wire (described below) I called a local anodizer to see if I could beg or buy some aluminum wire from him. He took two days to call me back and then quoted me a price of $30 for about ten feet of wire. I said aluminum not gold !! I kept looking.

In any case find a supplier of dyes and ask for samples. The dyes are powder and I got a small amount of black, red, green, blue, gold, bronze, and yellow. Some of them are tremendously expensive and you only need about three tablespoons to make a gallon of dye, so you don't need to buy a pound for several hundred dollars that would last a thousand years of home use. Black is about $50 per pound - red is a couple of hundred (I was told). The dye solution is re-usable and apparently you just add a bit more powder when say your black turns a bit blue. I haven't yet.

Mix the dye according to specs. The solution is supposed to have a particular PH and I got this with some litmus paper strips and found that it just meant adding a couple of tablespoons of household vinegar to the gallon of dye. It MIGHT be necessary to be accurate here but I DOUBT IT.

I use an old two gallon stainless cooking pot and a one element hot plate for the dying step. DO EVEN THINK OF DOING THIS IN THE WIFE'S KITCHEN. The dye is very nasty stuff and is IMPOSSIBLE to get out of anything it touches. Stainless is the name of the game here.

My dye instructions say the dye should be at 130 degrees (I think). The important thing is not to heat it anywhere near boiling or the pores in the oxide layer of the part will seal up and the dye will not take. The part almost immediately takes the black dye I have although I believe about 20 minutes is recommended in the solution with the part being stirred to keep fresh dye moving around.

After dyeing the parts, the parts should be put into clean boiling water and boiled for about another 1/2 hour. Keep the water boiling. This seals the part. I have heard on this list that there is something that should be in the water to aid the sealing process. Maybe someone could repeat this. I don't use anything and I have good results. My black parts come out looking like they have been professionally black lacquered. In fact much better that I've seen from a lot of commercial places.

I haven't quite determined how much parts should be machined undersized in order to maintain fit. I do know that I had a piece of tubing that was machined to fit inside another and I had a nice sliding fit before anodizing and they wouldn't fit afterward. I had a hell of a time hand sanding he one piece down to fit (600 paper). The surface was VERY HARD, but I did manage it and the part is still relatively shiny. I probably only took off about 1/4 thou, I don't know.

That's about it - give it a try. It's a pretty forgiving process.

I'm sure I'll hear about all the stuff I'm doing wrong from some of the commercial anodizers out there. It was more of an experiment for me - one that I'll keep cause it works so well.

Just be careful eh !! (Canadian)

Dave Sage

[a few more questions and answers regarding Dave's article]:


> If it comes out poorly, is
> there a way to reverse the process? As long as i've not sealed
> it, does it come off with some other chemical?

Even after the part has been dyed the whole mess can be removed with a caustic (soda) solution (or lye I suppose), with a corresponding dulling and etching of the finish.

[he also wrote, responding to a similar question]:

Anodizing is VERY EASILY stripped off using a mild Caustic solution - aka household lye. Start weak and watch for the dye colour to disappear. Watch carefully, the caustic also eats aluminum quite nicely. Flush well with water and wash with dish soap. The part may be a milky or stained colour after but the re-anodizing process will (in my experience) return it to an even finish again. You could polish the part first as well with 0000 steel wool and/or 600 wet/dry paper.

[and one more question/answer]


> When you are anodizing Al you have to attach the peice to the
> power supply. Does this leave a blemish on the article.

You must use aluminum wire or some sort of aluminum clip. Never use steel, copper or anything else. It will disintigrate quickly.

Assuming you use aluminum wire, the blemish is very small and usually un-noticeable. Have a look at some commercially anodized piece you may have around. The marks are there somewhere and may only be the size of a pin prick. There is always more than one because the wire is usually wrapped in and around the piece. The size of the blemish is only as large as the contact point between the wire and the piece. Since the wire is round and it usually touches the piece on an edge or something, the point of contact is actually SMALLER than you think. In a lot of cases there is usually a hole in the piece and if you put the wire through the hole the point of contact will be on the edge of the hole. If a screw is normally in the hole it will hide the mark.


> I have read about Alligator clips, Wrapping the peice in wire,
> drilling and tapping a hole to attach to. What is the best
> method for not leaving any marks or blemishes.

In almost everything I have built so far I usually have a threaded hole somewhere. I find that the best and simplest connection method is to FORCE thread the aluminum wire into the threaded hole. In this way the blemish is large but is then inside the hole and not visible when assembled.

You must understand that the aluminum wire I have is probably # 14 guage and is VERY soft aluminum. So soft that it can be stretched and broken so it threads easily into 6061 T6 tapped holes without damaging them. Sometimes doubling the wire over first is necessary to make it large enough to thread in.

Failing that, the wire can be wrapped and twisted but the connection MUST be VERY tight and if you jiggle the part while it is hanging on the wire and you feel it move the connection is not tight.


> assuming I want to anodize a square block of alloy with no where
> convenient to clip to

This type of shape is difficult. Just do your best to wrap the wire around it - perhaps in several directions and twist the wire tight. The blemishes will only be at points of contact.

As a point of interest - in applications where VERY large numbers of small parts need to anodized and blemishes are not a big concern the parts are piled into an aluminum cage and a weight is put on the top of the pile. The parts are then all connected to each other tightly by multiple points of contact where they touch. They all anodize just fine except where they touch. After dyeing the parts are examined. If there are any with unacceptably large blemishes they are simply stripped of their anodizing with caustic solution and re-anodized with the next batch.