titanium colorization - anodization anyone?

[hackR]

i found this article in a google search for a way to colorize titanium...

a certain engineer-run-amuck (you know the same one that gleefully destroyed a rolex case in the name of metallurgical forensics ) and i have a couple 172 Tantalums that we plan to play with to get the colorization of the case to the correct tantalum color...

notice the use of the word 'we'... ...i'm just the sourcer and a googler...

here's the link: Anodizing titanium

here's a quick cut/paste of the article:

This article assumes that you already have an anodizer, and just need some hints on how to use it

Use rubber gloves to avoid electrocution. Follow all normal high-voltage handling guidelines.

You need an electrolyte solution in a non-conducting container.

TSP (trisodium phosphate), ammonium-phosphate, and Borax are among the chemicals I've used. TSP is found in the paint department (for washing walls). Ammonium phosphate is a lawn fertilizer. Borax is found in the laundry aisle (non-chlorine bleach). It's not really critical what chemical or how strong, but avoid chlorides, nitrates and sulphates. For either TSP or Borax, about 5g/l is a good concentration (about 1/10 of saturated). Remember: The water is what does the work; the salt or acid is just an ion source.

NOTE: Environmentally sensitive people worry about TSP and the environment. The electrolyte is not consumed. Several years of anodizing would release as much phosphate into the environment as a single load of laundry or a single treatment of ChemLawn. TSP is only bad if it gets into the aquifers: Just don't pour it down the drain! Save it for reuse, or dilute and spray it on the garden.

I use a Rubbermaid® storage container because they resist chemicals well, last a long time, have lids, and are available everywhere.

For the Cathode (negative electrode): Use a scrap piece of metal immersed in the solution. I use a loosely coiled titanium wire, but anything non-rusting should work.

Rule of thumb: The immersed surface area of the cathode should be greater than that of the anode (work piece).

In use, hydrogen will bubble off of this piece. For large pieces, make sure you have adequate ventilation to avoid an explosion hazard.

Attach the piece to be colored, the work piece, to the anode (positive electrode). It must be free of oils. I often wipe things down with acetone or alcohol to make sure they are clean. Don't allow any non-titanium parts of the anode circuit to touch the solution. I often lower my pieces into the solution on a titanium hook, or with titanium tongs (both homemade).

After the piece is immersed, adjust the rectified, regulated, (protected, fused) voltage to get the color you want (between 25-120 vdc).

Color is voltage dependant. For bigger pieces, it just takes longer. Or more current. Use fuses, an ammeter, and/or a power resistor (or a light bulb in series) to avoid burning out your anodizer.

Color Guide: The exact voltage it takes to get a particular color depends on many variable factors such as free-ion content of the electrolyte, surface finish of the metal, stability of the voltage source, and so on. If you want 2 pieces to exactly match, anodize them at the same time. As a rule of thumb, the spectrum is that shown in the MrTitanium logo. The first tinge of bronze appears at around 18 volts, the near-white blue is around 50 volts, and the bright green is around 110. There is no true red, and the dark blues and violets are sensitive to fingerprints. See my Physics page for more details about how and why the colors work.

Never let the anode and cathode pieces touch each other; short-circuit welding is a technique not covered here.

[lanikai]

I like the "don't" forget the rubber gloves bit..

Borax sounds interesting..

I think I'll stick with Oxi and leave the voltage to you R ... I survived one heart issue last year..

Looking forward to your results though

AC/L

[redwatch]

Cool info R! Can't wait to see the results! (assuming the royal "we" plan to try this out?)

[kbiz]

or you could just send it out to an anodizer

[Bike Mike]

This is going to be fun!

Now just need a sexy lab assistant!

[Bike Mike]

So in the pursuit to create the perfect Tantalum looking Pam's, I contacted one of my metal supplier shops for some actual Tantalum. The smallest plate I could buy, was 1" X 12" X 24" which weighs in at 173lbs. goes for the bargain basement price of $10,360!

Anyone want to make a donation?

[Drulee]

Any update yet? I'd love to see how this turned out. This, and some lead fishing line weights in the case, will make my 172 even more "Tantalum like"

[McRae]

A simpler way of doing this is just heating the titanium, it changes colour when heated. Look at pictures of an exhaust made out of titanium for inspiration. There's probably an list at what temps different colours emerge if you google.

I normally do it on titanium bolts, make them bright blue, so I don't mix'em with other stuff when panic strikes...

[Bike Mike]

No updates as of yet

[Drulee]

Hmmm, I may just toss a couple of skinny titanium CGs in the oven, and see what happens

[McRae]

Yeah, I normally use a welding torch, since I don't care about getting a even result, but for this you need a little more control... An oven as Drulee mentioned can be one way, if it's enough heat?! Otherwise I know that jewellers use a kind of melting oven (very small), that probably can go much higher in temps.

[DocRaph]

Hi,

I had a project at work recently, where we wanted to use anodizing on Titanium parts to use as a wear indicator.

The theory was that since the color you see is related to the thickness of the oxide layer, as the oxide layer wore down then the color would change.

That was the theory - getting it to work was a lot of work.

First the electrolyte - we tried borax, sodium tri-phosphate and even Coca-Cola. They all worked pretty well.

The depth of the oxide layer which gives the colors is controlled by voltage and not current, so we hooked up a couple of lab bench power supplies to give us the total range of voltages required (I'll look at my notes at work tomorrow and let you know what voltage gave what color).

For both anode and cathode we used Titanium mesh, to give plenty of surface area, and also to rests the test piece on.

The first problem encountered was the surface finish of the Titanium - we tried polishing first, which is extremely difficult due to the softness of the metal causing it to 'gall' with the fine polishing particles.

Got a polished surface eventually - gave very washed out colors when we anodized.

We then tried a rough brushed surface - much better, but highlighted the brush lines.

Grit blasting - fine grit gave a matt surface which gave a very good result.

Acid etching gave us the best result, but the mixture of acid is not something I would recommend outside a lab (includes phosphoric acid!)

After we anodized some parts we started wear tests - in general use the anodizing scratched off in places long before we saw a color change - oh well.....idea abandoned (but not the equipment and chemicals - at some point I will dabble again).

Did come across an article when we were researching technique, which involved Coca-Cola, a 9-volt battery and a paint brush - apparently it worked!!!

We did consider heat as well, but you need extremely good temperature control in an oven with no temperature gradient or air movement or you will get a range of colors on any surface larger than a square centimeter.

Have fun experimenting (Titanium is much cheaper than Tantalum but apparently easier to anodize - the range of voltages is not as high).

Cheers, DR

[hackR]

Mike and Raph are going to have fun together...

[Drulee]

I want further info on the 9V Coke painting technique

[DocRaph]

When I was researching anodizing techniques I came across absolutely lots of references.

Try this one - http://www.popsci.com/diy/article/2005-06/titanium-technicolor.

Or just Google 'titanium anodizing cola' to bring up tons of info.

I've found the report I did and am cutting out some of the data and images to post - got to be careful I don't let any company sensitive stuff get out.

I've also got hold of some more Titanium (not so easy to get it in the UK - really expensive!), so I'm going to play around with the anodizing a bit more - will let you know how it goes.

Cheers, DR

[Bike Mike]

The issue with anodizing titaium, is that it is more of a decorative coating that has solid uniformity in color then what Tantalum is. You can see in the picture below.

Ti Anodized:

More here: Linky

Tantalum watches:

By looking at the pics, I think you can gain a understanding of the difference between Anodized Ti and what Lani has done. Just need to control the amount of blueing...which I have some ideas on while keeping the oxide layer dark.

Raph I am liking oyur style!

[DocRaph]

I'll get the reduced report on Monday when I'm back at work, however from my notes at home I have an image which shows pretty well what I got color-wise.

From it you can see that grey appears below 10 volts DC, between 60-70 volts DC, then finally at above 150 volts DC.

The color that you see from the anodizing is directly related to the thickness of the oxide layer, which is translucent and refracts the light by different amounts - a bit like oil on water.

Naturally occurring Titanium and Tantalum oxide layers will be fairly thin. They will build up in time until they totally cover the exposed metal, then prevent any further oxidation to take place - that is why it goes grey and stops.

When you anodize these metals, you actually force the layer to be thicker to get the colors.

To get an accurate aging color you will need to either anodize below 10 volts DC, which is quite difficult to get as you need to get the potential difference across the volume of electrolyte to get the process going.

I found with a large container the minimum at which I could get anodizing to work was about 12 volts DC - which gives a straw color - I can see where brushing would be useful in this case.

The alternative would be to anodize above 150 volts DC (risky-ouch), where you will also get a gray color. (60-70 volts DC gives a sort of blueish-gray)

This is the oxides' maximum thickness and it is pointless trying raise the voltage past this point as it does not change any more (I went up to 250 volts DC)

Catch you later, DR

[DocRaph]

I've just had a look at my Panerai SE1997-2007 book.

In it are both the PAM172 Luminor Tantalum and the PAM192 Chrono Tantalum.

Both have brushed Tantalum cases, polished Tantalum bezels, but they also both use brushed Titanium case-backs, exhibition for the Luminor and solid for the Chrono.

As you can see, there is only a very light difference between the brushed Titanium and brushed Tantalum, with the Tantalum being ever so slightly darker.

As long as you manage to get a darker grey for the case by anodizing than the brushed Titanium back, all should look correct.

To maintain the difference, just keep the back brushed clean of thick oxide layers frequently, preferably with it removed so that you do not accidentally polish the case.

Coincidentally, one of the options I looked at for my project was Titanium Nitride coating - heating the Titanium up in a Nitrogen filled oven can give you a nice dark gray layer of Titanium Nitride, which is much harder than the Oxide (also the reason why I didn't pursue it- we wanted to find wear by color change - not no wear).

Might be worth considering if you can get access to an oven with a Nitrogen purge.

Cheers, DR

[Drulee]

The alternative would be to anodize above 150 volts DC (risky-ouch), where you will also get a gray color. (60-70 volts DC gives a sort of blueish-gray)

This is the oxides' maximum thickness and it is pointless trying raise the voltage past this point as it does not change any more (I went up to 250 volts DC)

Isn't the blue/grey colour accurate for mimicking a Tantalum look?

EDIT: Woops, forgot to hit refresh, so I didn't see your latest post.

I believe they had to use Titanium backs as they ran into too many problems trying to thread and machine a Tantalum one, could be wrong though. Also these pics aren't that great - notice the hatch pattern easily seen on the case and band.

And if they are from that site "PaneraiSource", I definitely wouldn't trust them.

Here are some more pics:

[FxrAndy]

well 30min at 300 deg c makes it go gold, i will let you know what color it is after an hour

[DocRaph]

Sorry aboput the pics - they are from the Special Editions brochure, but I only scanned them at 300dpi, which results in the cross hatching.

I've seen Tantalum jewelry which has been oxidized and contrast polished (nearly bought a Tantalum wedding ring), and the oxide is dark gray rather than blue grey, however the polished Tantalum certainly has a bluish tinge to it under certain lighting conditions- much more so than Titanium

You're correct about the machining. Titanium is an absolute sod to machine, and Tantalum is about 10 times worse, so putting a fine thread on Tantalum is asking a bit much.

Just thinking......even if you get the color correct.......what about the weight??????

Titanium has a density of 4.5 g/cc.

Tantalum has a density of 16.4 g/cc ... 4 times heavier.

Just for comparison, Gold is 19.3, Iron is 7.9, Lead is 11.3, Nickel is 8.9, Palladium is 12.0, Platinum is 21.5 and Tungsten is 19.3.

Stainless steel is between Iron and Nickel.

I suppose you could use a 'look but no touch' policy, or put a really heavy bracelet on it.....

Have fun...

Cheers, DR

[prdubis]

Just spent the afternoon trying to oxidize my 172 with Oxyclean...Did everything as explained...

AND IT'S A COMPLETE DISASTER!!

SS is not supposed to be oxidized but it became brownish, as the case did...

I guess this case is dead!

It was coming from DSN, don't know if he uses real titanium, or if the crown guard and bezel were really made of SS...

[FxrAndy]

300degrees centigrade 1 hour

Polish with cape cod to get it back to what you were going for

More pics to follow

[FxrAndy]

Quickly assembled sorry the light does not really highlight the difference in color but it is there, weather it is the right color or not it is an attempt

Pr Dubis have to tried cape cod ?

[DocRaph]

Looking at using heat to color Titanium - came across these links:-

http://www.hollygage.com/pages/adding_color_to_titanium_with_a_torch.html

http://www.artmetal.com/files/imported/project/TOC/colorRMS.html

Further to my mention of heating in Nitrogen, I did come across some notes I made -

By heating the Titanium up to approximately 1,200 degC (2,192 degF) in a furnace with Nitrogen purge and in the presence of Carbon, a dark grey coating of Titanium Carbo-Nitride will be formed.

Short exposure times give a gray coating, longer exposure gives a dark gray coating.

This is the same material that is vapor deposited on knives, etc as a tough protective layer.

Which also reminds me - if you keep on heating Titanium, just in air, you will see the colors change as the oxide layer gets thicker, until it reaches gray, when it will stop - that is the maximum thickness of the oxide.

If you need to try for a different color just polish the oxide layer off and start again. (Exactly the same as anodizing).

Cheers, DR