Alkaline Anodizing of Titanium
(photo courtesy of Russamer Lab)
Q. We want to anodize titanium using an alkaline anodizing bath. Who can give use the formulation of a alkaline anodizing bath. We want to get a gray coating.
Any advice would be appreciated.J.H. Pennings
TNO Institute of Industrial Technology - Netherlands
A. See AMS 2488 [link is to spec at TechStreet] - the anodizing is performed in an alkaline solution of pH >= 13. Unlike anodizing aluminum, the colour is not uniform and not controllable (almost). Depending on the alloy (and solution?!), we are getting yellow to blue through grey appearance.
captive metal finisher - Montreal, Québec, Canada
A. With titanium in a bath of trisodium phosphate you get the most beautiful color of blue imaginable. All you need to do is to immerse the part, turn on the current and voilà , bright blue. Not gray but close?Dave Fairbourn
- Sandy, Utah
A. Thanks Dave. To minimize confusion, though, we need to tell the readers that there are two general types of titanium anodizing. The "alkaline anodizing" that Max speaks of is a heavy, wear-resistant, anti-galling surface for engineering applications. The acid or neutral anodizing you are describing is a very thin very colorful diffraction coloration for decorative jewelry and similar applications.
Ted Mooney, P.E. RET
Brick, New Jersey
A. A true grey from TSP (trisodium phosphate) is not probable.
Brown, blue, silver, yellow, purple and green are possible at voltages up to 200. There are several different shades possible for each. Precise color requires precise voltage control. It anodizes nearly instantly. Surface prep makes a significant difference in the luster or look of the product. Does not need any further protection after anodize.
From 10% to 3% solutions are recommended.
Q. A magazine called Xtreme R/C Cars will publish an article on titanium anodizing in an upcoming issue. Sorry I don't know what month, but issue 4.9 I think. I am interested in titanium & alum anodizing, and would like to obtain a red color. Any info is greatly appreciated.David Thomason
A. The color red is not possible with titanium anodizing nor is black. Apparently neither exists in the spectrum created by the oxide layer formed on the surface. The color exists only as reflected light.Dennis Rand
- Plymouth, Massachusetts
Q. I am anodizing a 6al-4v titanium medical device blue, yellow & green. These parts are subjected to 250 F steam autoclaving for sterilization. Some of the parts after two cycles of autoclaving (40 min/cycle)are beginning to change to the next color. (yellow - magenta, blue-clear). This is only happening in a few parts but I need help into why it is happening and how to stop it. If anyone has suggestions I would appreciate the help.Jim Johnson, Sr.Design Eng.
- carlsbad, California
A. We can produce and reproduce stable and controllable colors for titanium anodizing. Technology is ready for licensing.
You can see shades available on our web site. Black color can be obtained also, but this is a different technology.
Q. Dear Sirs,
- Delhi, India
Q. I am new to the anodizing process and am having problems anodizing titanium green. The pieces are about 2 and a half inches long and are a half inch wide. When I anodize these pieces in other colors I have very little to no problems. I was wondering if this could be environmentally affected (humidity) or is this a normal problem for larger pieces.Terry Donnalson
hobbyist - Lititz, Pennsylvania
Bioscience and Bioengineering of Titanium Materials
Q. Alkaline Anodizing of Titanium Ti-6AL-4V. I am looking for the exact bath solution for what I have been told is a type II anodize per AMS 2488 [link is to spec at TechStreet]D.
I understand that it is >=13 pH and that the temperature is controlled to +/-2 F and that voltage is the controlled characteristic, but WHAT is the chemical?
medical device industry - Huntington, Indiana
A. Hi, Vicki. I know it's strange and you'll say "how can that be?", but ...
... even though the alkaline anodizing process is covered by AMS spec ...
... some of the details of the alkaline anodizing process are trade secrets. You have to figure out these details for yourself, or you have to retain a consultant who will give them to you; you won't find them in the literature or in a public forum. Sorry, and admittedly it makes little sense, but there it is :-)
Ted Mooney, P.E. RET
Brick, New Jersey
May 2, 2008
Q. Dear sir,
- Bangkok, Thailand
December 7, 2008
Q. We can do titanium anodising Green, Blue, Purple, silver, etc.
titanium - Ningbo, China
The Encyclopedia of Jewelry-Making Techniques:
February 12, 2009
I wonder if someone could instruct me as to what solution is best to achieve an anodized silver finish on 6AL-4AV grade 5 titanium.
I would also appreciate information on setup and procedure i.e. precleaning procedure, anode/cathode ratio, suitable materials for cathode and jigs. I also need information on voltage/time and amps.
I would be very appreciate if anyone could provide this kind of information.
- Birmingham, west midlands, United Kingdom
August 17, 2009
Q. We are doing golden, blue, pink, green, and yellow -- but how to do black colour?manoj pavasiya
- Bombay, India
A. I see several comments pertaining to Grade II Titanium and obtaining green color.
Grade II in volume on racks can be vexing.
A common defect is a failure to obtain even color
Color can have a 'Ghosty" appearance when viewed inclined and under a bright light.
A coupon anodized, resulting in an uneven green color. When measured, the oxide thickness is uniform over the coupon.
Theories are, a change while anodizing of the um/Volt applied, and/or the um/second.
According to theory; these changes result in an anodized layer of mixed Titanium Oxide of TiO2, TIO3----X
Another theory is a change in cubic structure; i.e. anatase to rutile.
I call it The Grade II Blues.
- Minneapolis, MN
May 31, 2012
Q. I am doing Ti-6AL-4V type II anodizing, but a few days ago during the process, the parts got a pink color and then the type II anodizing process stops in the parts but not in the titanium racks.Tatiana Rios
medical instruments - Medellin, Colombia
A. Type II titanium anodizing will have uniform gray color. Some companies produce anodized parts covered by "fur" that require additional removal step. We produce hard anti-galling coating clean and ready for use. There is a possibility to grow the coating very thick for application where dialectic surface is required.
The color anodizing is always thin, and can serve mostly for color coding. The uniformity and consistency of color anodizing depend only on initial surface activation. This step can be conducted either electroless or under electrical current in a separate tank. Both methods are fine. As soon as the titanium surface is ready, it does not matter what anodizing solution you select for the final coloring. It can be oxalic acid or sodium wolframat or similar solutions available from the vendors. Be sure to final rinse the colored parts in diluted alkali solution, in order to prevent colors fading.