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topic 7926

Anodizing titanium to green color -- Q&A's




An ongoing discussion from 2001 through 2015 . . .

(2001)

Q. I have done anodizing on titanium. The blues are easy to achieve. I have been experimenting and trying to get greens but have not yet been successful. Perhaps some one could suggest the correct solution and voltage to help me out.

Thanks.

Todd Huehn
plating - Blaine, Minnesota


(2001)

A. It takes very nearly 200 volts to get green. This is serious voltage. Make sure that you have an isolation transformer in the circuit and you have quick blow fuses of the appropriate amperage on the output side. A volt or two will make a fairly significant difference in the color for whatever solution that you use, so experiment.

James Watts
- Navarre, Florida


sidebar (2001)

Q. When you anodise titanium, does this then increase its corrosion resistance? How stable is the blue oxide layer in an acidic environment?

Regards,

Steve Van Smaalen
steel - Port Kembla, NSW Australia


Hi Steve. In general, metal oxide coatings do not increase acid resistance because oxides tend to dissolve into acids quicker than raw metals. I don't think titanium is any different than most metals in this regard, but if anyone feels differently, please let me know :-)

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2001)

A. My experience with Titanium anodizing showed that you get different colours with the same voltage, on different titanium alloys. Therefore one cannot exactly say at what voltage you'll get what colour... unless he has experience with the same alloy. Also.. different colours will be obtained depending on what has been done to your part... e.g., embossing will affect the colour which you'll get badly.

Mark Camilleri
- Malta


Corrosion Behavior of Anodized Titanium Nanotube Used in Implant

(2002)

A. Color anodize on titanium is fairly straight forward. What is not is obtaining a coating that is biocompatible. Contrary to popular belief the solution and cell play a role. I for one am fearful that shops jumping into the market will kill it by offering any finish produced as implantable. This is not a paperclip or nut and bolt market.

Jon Quirt
- Fridley, Minnesota


(2002)

(harrumph)
Parts is parts.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



To minimize searching and offer multiple viewpoints, we've combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



Green anodizing of titanium sword

(2005)

Q. I have been trying to acquire some titanium (which is remarkably hard to buy) to create a katana to anodize green (it just seems like a interesting thing, I'm in 9th grade (15 years old) with my parents permission, but I can't seem to find the right voltage. My friend let me try his but all I got was dark blue sort of stuff.

Nathan Figueroa
Student - NY, New York


(2005)

A. In USA you can buy small quantity of titanium from Reactive metals studio. They sell anodizing equipment and booklet too. Good luck!

Goran Budija
- Zagreb,Croatia


(2005)

A. To get a green colour on titanium is hard - it is the last colour you get with anodising as you raise the voltage before the oxide layer goes grey, and with some alloys you don't get a green at all. It usually takes about 70-90 volts DC, which can give you a nasty shock, so wear rubber protective gloves [linked by editor to product info at Amazon] and avoid anything that could cause a short circuit. However, if you are fully aware of the safety precautions, then try it, with adult help. You need to make the titanium the anode and use a piece of stainless steel as the cathode. For the electrolyte I use dilute sodium or ammonium sulphate or phosphate solution. I estimate that a strength of about 1 gram per 100 ml would be enough. If it is too concentrated, a large current will flow and you can get sparking as you lower the sword into the electrolyte - quite dramatic, but not good for the oxide colours ! The best way to get the colour you want is to gradually increase the voltage while taking the metal out to check it. Sometimes each colour takes a couple of minutes to develop. The sequence of colours from 5 volts up is brown, purple, dark blue (20 V), light blue, yellow (40 V), gold, pink (50 V), magenta (pinky purple), emerald green (70 V), apple green, grey. Good luck !

Jeremy Wyatt
- Epsom, Surrey, England

Ed. note: To emphasize Mr. Wyatt's cautions, this sounds like a good idea for a science project that can be done under the supervision of your science teacher. Not all adults (in fact few adults) are trained in safely working with electricity, and these voltages are definitely not innocuous.




Flared area of titanium tube turns black instead of anodizing

(2006)

Q. I am trying to anodize pieces of 7/8" diameter 1/2" long 6-4 Ti tubing. The green colour is problematic when I anodize flared sections of the tube. The non-flared areas seem to colour just fine. The parts are high polished, and surface roughness doesn't seem to matter when I try obtaining the green colour, it just looks "blackodized" in the flared areas. I've tried various solutions, but to no avail. I think it is being caused simply by the shape of the part. Does this make sense to anyone? Any help would be appreciated.

Jeff Swayze
Hole Joy! - Kelowna, B.C. Canada


Jewelry: Concepts and Technology


A. Hi Jeff. I don't believe that the problem stems from the shape. Perhaps the tooling that does the flaring involves heat or oils that are spoiling the effort. I would scrub the flared area with powdered pumice and detergent and see if it makes a difference. Maybe see if it's possible to bend that tube by hand, and if the stretching alone has caused some metallurgical dislocation that causes blackening at the bend. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Can't seem to green anodize titanium in sulphuric acid

January 23, 2008

Q. I want the ratio of mixing acid and the voltage to be applied. I am using sulphuric acid for colouring of titanium, and lead sheet as anode. So please tell me what I have to do for bringing green colour to titanium.

h.arivazhagan
- puduvai,tamilnadu,india


January 23, 2008

A. Hi, cousin Arivazhagan.
Jeremy has told us earlier on what voltage to apply, and that he uses dilute sodium or ammonium sulphate or phosphate solution as the electrolyte. I think the answer to your question then is to use dilute sodium or ammonium sulphate or phosphate solution at the voltage he suggests, rather than to ask what voltage and what ratio to use for sulphuric acid :-)

Good luck.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


March 31, 2009 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi,
My name is Prashant R.Pillai.
I am in the research of colouring of titanium. I have successfully managed to colour titanium in bronze, blue and yellow . After many trials I am not able to get green colour even at 110, 120 & 130 Volts.
So please do suggest the best medium and voltage to get this colour.

Prashant Pillai
student - Pune, Maharashtra& India

February 2015

Hi cousin Prashant. People will rarely take the time to re-post their reply a 2nd time if you ignore their first posting; so please try your best to frame your ongoing questions in terms of the answers already offered on this page and preceding your question. Thanks.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


August 13, 2009 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Please help~
One of our medical products (titanium washer) is required to be anodized in color green and gold. The gold one works fine, but the green ones all failed.
Below is the letter from our supplier.
We are told "as the crystallites broke out along turning grooves a possible cause can be a high temperature treatment were titan changes its crystallite structure between £\ and £] phase."
Can someone help to explain what could be the root cause?
Any suggestion to solve the defect like this?

The parts have been activated prior to the coloring in a pretreatment process, POLINOX TB 100, to remove the Ti-oxide layer.
Then the parts have been colored according to the order information.
After this process we have observed an inhomogeneous color on the surface on parts.
We have stopped the production and analyzed the situation.
We have found that the activation process removed non homogeneously material along circular grooves.
The result is shown in the pictures and is visible as non homogeneous surface structure.

Thank you in advance~

Alice Chao
Manufacturer - Taiwan

----
Ed. note: Sorry Alice, we have no pictures from you.




December 4, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread



Dear All,

Can anybody tell me, why there is so many problem created for obtaining green colour in titanium anodising.

Thanks
Rahul

Rahul Ghagare
- mumbai, maharashtra, India


January 2015

Hi Rahul. As you see, we appended your inquiry to a thread on the subject, which should offer some helpful info. Letter 1265 also addresses this topic -- see the postings on that letter from Jon Quirt and Anna Berkovich. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


January 14, 2015

A. Green is very difficult to obtain. I start by buffing the material to a very shiny state, then removing all buffing compound with acetone, alcohol and ammonia.

When it is very very shiny and surgically clean, I suspend in distilled water. I do not touch with hands anymore -- use medical disposable gloves from thereon.

You'll need to etch it next. I use multietch at about 150 °F with a fish tank air bubbler for agitation. I then etch in this solution (make sure it's fresh, can't reuse it more than once or twice). I let it etch for about 7 seconds, then quickly remove and immerse in distilled water, then wipe it down with a lint free cloth (etching too long removes finish).

After it's clean again (remember no touching) -- I reuse the ammonia; here it goes back in distilled water.

To get green I find I need somewhere between 95 and 120 volts DC depending on alloy and other factors (such as preparation). I use 7% phosphoric acid in distilled water. I refrigerate this and even place acid bath in a container of ice so it stays cold.

Put in the piece, use voltage like I said, don't let any part of the electric lead get wet (this can be tricky and require creation of creative fixtures.)

Remove it, it should be green. Start with low end of voltage range and increase until you get the green you want. If you prepare the items for this process methodically, same way every time, you should be able to achieve similar results on similar alloys.

Christopher Susie
- Baltimore, Maryland USA


December 21, 2015

Problem of achieving green colour is in the solution. In higher voltage you must keep high diffusion. I recommend solution of 0.1 H3PO4 or any NaH2PO4, Na2HPO4 works best, and easily achieves green at about 120 V. By addition of Fluoride salts you may drop down voltage into 90 V. But remember to keep the low amount of acid around 0.1-0.2M.

Marcin Klomski
M&K - Gdańsk Poland


December 2015

thumbs up signHi Marcin. Thanks for the great specifics!

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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