Simple method of black anodizing aluminum wanted

A. Sir,

Without using commercial products and with no experience in anodizing, it is not very likely that you will obtain "no size change and good results" on black anodizing. It is not worth the disposal costs for a few pieces. Recommend you contact a small commercial shop.

A. You say you have access to chemicals; what about a rectifier and cathodes? And other equipment necessary for anodizing?

I agree with the above response: contact a small commercial shop.

A. The Bendix Corporation's Teterboro, New Jersey, $3 Million/year, military specification, multilayer printed wiring board facility, and captive anodizing, plating, and casting impregnation shop was started in the 1950's by a few guys developing single sided laminate in 5 gallon tanks. Today, the same thing is possible, except you won't have the luxury of waiting twenty years before strapping a waste treatment system to the end of the line.

The Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon affil links] (see our book section) is a good start to read about what you need. The new edition does not give the name of a black dye. Nigrosine JB was mentioned in a previous edition, but may be better off getting a sample of dye from one of the major suppliers.

Sulfuric acid anodize with a black dye, sealed with nickel acetate sounds like what you should investigate.

More as you happen.

For school purposes only, not to obtain a useful coating.

1. Clean in a solution of bicarbonate of soda, about 8 oz /gal, a few drops of liquid soap, and enough lye to make it fizz quite a bit at 140-150 F.
2. Dip in a 50% nitric acid solution for 5 - 30 seconds at room temp.
3. Anodize at 15 volts for 30 to 45 min in a 15% by weight solution of sulfuric acid at a constant 72 °F. This will require an ice bath. Use 6061 or 6063 aluminum cathode at a ratio of 1 to 3 times more part area than cathode area. Ramp voltage up over a minute or so.
4. dye with any dye stuff available, pH about 6, 130 °F for 30 min.
5. Seal in distilled water. Nickel ACETATE at about 1 teaspoon per liter will help. Boiling! for 15 min. pH 5.5 to 5.8
6. blow dry or air dry.

Rinse well between all steps.

Notice the temps are F, not C, and are very important.

It's a cruel, cruel thing that you did, Jim. I know for a fact that this is the very procedure used to anodize Sojourner parts :-0 . From reading letter 1217, you can also use sodium dichromate as a seal. Anyhow, we don't want to do anything useful in school! Get a bad reputation that way.

 Thanks Jim. I will try this method and, of course, I will not expect the best results. I'll let you know.

Perhaps is my limited knowledge in english (or in the stated method itself) the reason of not understanding why Tom got so angry about.

TI: Mr. Watts did a very nice thing, showing you a perfectly good method. I was only kibitzing with Jim. Now there is another English word:-) You should ignore half the things I say, (which half?).

But we don't want to hear that you don't expect the best results. It must be perfect. I just ran across a formula for nickel acetate seal, in case you cannot find a proprietary supplier. Nickel acetate 6 g/liter, boric acid 8 g/l. pH 5-6, made with deionized water, 70-90 °C for 15 minutes. Perhaps you can try the black ink that is used in the inkjet printers for a dyestuff.

A. To my knowledge aluminum cannot be nitrided (that's for steel). Anodizing is artificial "rusting" of the aluminum to develop a hard corrosion-resistant surface of aluminum oxide. You might look up "Nikasil", a coating made especially for engine parts (see letter #1671).

A. Nitride can be obtained on aluminum but is very costly if you try and do it yourself. The semiconductor industry nitrides silicone wafers and sometimes the parts that are used in the process are aluminum and get coated all the time from the nitride. And after a period of time it has to be removed because of the build up on the surfaces which become too thick to use. Might find a chemical engineer that is in the business of semiconductors and they might guide you the right way.

A. For a flat black finish you could try Birchwood-Casey Alumiblack ⇦[Aluminum Black on eBay or Amazon [affil links] available through gun stores. Or you could visit Ron Newman's sight on You Tube for simple step by step process. Hal

A. I went all over looking for Aluminum Black as the guy from Ontario mentioned. The gun shops said that they can't get it shipped from the USA anymore. I make rifle scopes and do special modifications to cameras. The product doesn't wear as well as real anodizing, but if you don't polish on it too aggressively, it's not bad. If you have an aluminum window frame manufacturer in your city, sometimes they'll take in small jobs and do it for you.

A. Hi Fernan. I couldn't find such a channel but that posting was from 11 years ago. There are, however, a bunch of youtube videos about home anodizing.

Regards,