Anodizing titanium: amps, concentration, contamination, setup, problems

A. Hello Jean. It sounds like no problem to me.

By the way, those warnings you refer to were in regard to anodizing of aluminum with SS attached, not titanium with SS attached. Aluminum anodizing is done in very corrosive sulfuric acid. I don't know what would happen if you immersed an assembly of titanium and stainless steel in a titanium anodizing bath; it might depend on what electrolyte you use.

Luck & Regards,

Dear Ted,

Thanks so much for weighing in! I really appreciate it.

Happy New Year!
Jean

A. Data for 6-4 Ti is not going to be the same as CP Ti. It also will not anodize as well because you are looking at 10% alloy. The aluminum will anodize at a much lower voltage than the Ti and will look different than the Ti. I think the Vanadium will not react or will dissolve. In short, I think you will get funky looking anodized parts.

You can get a how to do it manual from Reactive Metals Studio, Inc. in clarksdale , AZ

Jim

A. Ti6-4 surgical instruments are routinely anodized for color coding. The first blue color appears around 28 V. The exact relationship between color and voltage will vary with each setup. You will have to experiment. If you are using titanium clips to hold the work, the anodized layer on the clip will need to be removed mechanically or in a dilute (5%) HF solution (handle with care) between each run.

A. Mr. Adams, please see topic 937 for a good discussion on that.

A. I have experience with anodizing small parts in titanium (commercially pure grade 1 and Ti 6Al 4V) and niobium, but nothing as large as your part. The current densities that I use vary from about 5 amps per square inch to less than an amp per square inch. I suggest that you start out on the lower range to avoid accidentally etching the piece. I use a solution of 3-5% by weight trisodium phosphate [on eBay or Amazon] in water. Keep the solution below 80 °F. I get more vivid colors on the 6-4 than the cp titanium, probably because it seems to take a higher finish easier. If you do not already have a suitable tank, you might try anodizing the piece with a brush saturated with the solution connected to the positive lead and the piece grounded to complete the circuit. You could use a painter's brush with the metal ferrule wired to the lead and then insulate the handle for safety. Artists use this technique to paint on sheets of Titanium.

A. Dan,

I'm afraid we'd need more info to be able to properly answer your question. An anodizing line for an aircraft manufacturer might be $5 million and still be considered a very economical machine whereas some people who want to do anodizing in their basement feel that $59 is too much to pay for the power supply.

To play around and experiment you probably need only a power supply, some stainless steel for an anode, and a few beakers [beakers on eBay or Amazon] or plastic vats of some sort.

A. It takes from 0 - 240 volts to get the variety of colors. Exact voltage control is mandatory to reproduce the same color. It will work on castings, but not quite as well. It is not as bad as aluminum or zinc castings to treat. Going from a hot rinse to a cold rinse a few times before you start will tend to fill the pores with water rather than chemicals, so there will be less bleeding when you finish.

A. You can get a kaleidoscope of colors when anodizing titanium. Solutions of various electrolytes are used: sulfuric acid, phosphoric acid, sodium hydroxide, ... As stated above, the voltage and time applied as well as electrolyte concentration will determine the color produced.

Titanium anodizing is one of those finishing processes that very closely approaches "art"; it takes a lot of leg-work, tank work, trial and error. There are some very good finishing houses that have perfected the process in terms of color matching, etc... Your alloy is a common one and should present no special problem to anodize.

A. I doubt if you will ever anodize with that strong of an acid solution. Try using a 7% trisodium phosphate [on eBay or Amazon] in distilled water and you will have enough amperage to anodize and not exceed the shutdown amperage. This will also allow you to get to your 100 volts. A plus, it is totally non hazardous. Reason, it is less conductive. What you have now is the crude equivalent of a dead short.

A. Titanium can be anodized according the voltage in sulfuric acid, the same as aluminium , and the colour may go blue to violet to yellow around 40 volts.

Once I used styrofoam in MEK / methyl ethyl ketone to mask and it worked.

WHY DON'T YOU USE STENCIL ETCHING, IT MAY WORK (BUT NEVER TRIED).

GOOD LUCK AND GOD BLESS

A. There are two quite different types of titanium anodizing, Michael. There is a decorative anodizing used on jewelry that produces thin refractive films in attractive colors, which is usually done from solutions of mild acid, or TSP [trisodium phosphate [on eBay or Amazon]]. And there is a heavy anodizing done from an alkaline bath for the purpose of making the surface less susceptible to galling; this is often done to spec AMS 2488.

If you can tell us a bit more about what you want to anodize and why, we can probably help you narrow it down to which type you are looking for.

A. Michael,
You'll find many knowledgeable and kind people that take their time answering letters here. But regardless of how much help you may receive through this forum, without previous experience, it'll never be enough to set up a good level industrial operation almost from zero. It may appear very simple but involves years of hands-on and theoretical knowledge. I recommend you to hire a consultant.

A. Hi Nathan. Your question relates to one of those weird situations in the metal finishing world. Nowhere in my library of finishing books is anodizing of titanium mentioned, and AMS 2488 doesn't tell you what solution to use or how to do this process; that is a trade secret :-(

Originally Tiodize was the only well known company offering the process, although a number of other shops offer it now, and a few consultants can help you. But successful AMS 2488 titanium anodizing involves tricks and solution compositions that are not yet generic knowledge. Sorry, but you have to either farm it out, or retain a consultant who knows how to do it, or do a painstaking gleaning of snippets of info from a computerized literature search and develop it independently.

Regards,

A. Rinse water cleanliness is my first thought. Are you using tap or DI for rinses? Are your rinses flowing or recirculating, and does the operator spray the parts down as they leave the rinse tanks? What is your limit for rinse cleanliness? Are there potential sources of contamination from either inorganic substances (such as drag-in from prior chemical tanks) or hydrocarbons (such as cutting fluid haze in the air from equipment nearby)?

If airborne hydrocarbon contaminants are an issue, they can also affect chemical tanks. I have personally seen this in desmut and anodize tanks, as our shop shares a building with a large machine shop, and we have to do more frequent tank changes as a result. The presence of scorched-looking, greasy dark brown or black residue at the waterline of your anodize tanks would be one indicator of hydrocarbon contamination.