# Anodizing Titanium



## Tom Anderson (Jan 26, 2010)

Since I'm a new member here, I thought I'd share my mini-tutorial on anodizing titanium.

The photos show some of the knives I once built, but the principles apply to other titanium gadgets as well. 

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The process of anodizing titanium involves immersing the object to be colored in a container with a titanium cathode inserted and filled with an electrolyte. Passing a DC charge through the electrolyte solution will cause a microscopic oxide film to adhere to the part. The thickness of the oxide film determines the color.

Attached is a color chart that lists the various colors obtainable through the various effective DC voltage ranges:







Note that these colors can also be obtained by heating the part to create the oxidation, but that process is not as accurately controlled.

The equipment used consists of the following:

1. A DC power supply that has a range of 0 to 125 volts. The wattage (amperage x voltage) of the power supply will determine the size of the part that can be anodized as well as the speed of anodization. For most knife handles (approximately 6” long or smaller), I would recommend using a 1-kilowatt DC power supply (approximately 7 amps x 150 volts).

2. A non-conductive container, large enough for the cathode (see #3) and the part to be anodized.

3. A strip of titanium to be used as a cathode. The surface area of this strip must be greater than the surface area of the part being anodized. For safety, the cathode can be covered with nylon webbing to avoid accidental contact with the part during immersion.

4. Electrolyte solution. This can be a simple solution of 5% trisodium phosphate in distilled water – enough to fill within 1” of the top of the container.

5. Leads for the + and – terminals between the DC power supply, cathode (titanium strip), and anode (see below).

6. Anode: This is a small hook made from titanium wire to which the part is attached for immersion.

7. Thick rubber gloves to be worn as a safety measure during the anodizing process.

8. A bottle of cleaner (Windex ammonia-based window cleaner works well).

9. A small paintbrush with a metal ferrule. This is used for reverse-polarity brush anodizing described later.


Equipment setup and use:

NOTE: Exercise caution when working with the power supply turned on to avoid electrocution. Always wear rubber gloves when the power supply is turned on. Do not attempt this process while working on an electrically conductive surface!

Fill the container with the 5% TSP/distilled water solution (electrolyte). Attach the cathode (-) lead from the DC power supply to the cathode – making sure the connection is well above the electrolyte level.

Attach the anode (+) lead to the titanium hook. Exercise caution not to bring the two leads together.

Turn on the power supply and adjust the voltage to achieve the color (as shown on the attached chart). Turn the power supply off.

Clean the part to be anodized with the ammonia based cleaner. Attach the part to the titanium hook/anode, and submerse it in the electrolyte bath.

Turn the DC power supply on until the color appears on the part. Turn the DC power supply off when the color is achieved and before removing the part from the electrolyte bath.
Re-clean and dry the part to remove any traces of electrolyte.

Multi-Stage Anodizing:

Applying different colors to a titanium part can be achieved using the equipment listed previously with several different techniques. Besides ensuring safety, the most important thing to remember is that the oxide film (color) applied during a higher voltage session will remain when applying an oxide film (color) at a lower voltage setting. For instance, you can submerge a titanium part that had been partially masked when a 40 DCV color (powder blue) was applied and apply a 25 DCV color (purple) without affecting the powder blue color.

I have attached several photos illustrating the results of various multi-stage anodized titanium parts.







This knife has had multi-stage anodized scales that were accomplished with the following (basic) steps:

1. Anodize the engraved bolster area with gold at 15VDC. Sand off the top to make it look like gold-filled engraving.

2. Mask off the engraved bolster area, apply a light coat of spray glue to the “overlay” area.

3. Anodize the light blue color at 43VDC.

4. Remove the spray glue and reapply another light coat.

5. Anodize the dark blue color at 28VDC

6. Remove the spray glue.

7. Anodize the purple color at 19VDC.

NOTE: All parts were anodized using the immersion method described previously. The stepped pivot screw collar is a separate piece, anodized at 28VDC.







This is another example of multi-stage anodizing. Here the overlays were anodized at 65VDC to achieve the green-gold color in the file work. Then, the tops of the overlays were sanded, cleaned, and re-anodized at 28VDC to achieve the blue color.


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## Tom Anderson (Jan 26, 2010)

Reverse-polarity anodization:

This is another technique using the same power supply and electrolyte, but using a paintbrush with a metal ferrule to “paint” the color on the part. The negative lead (cathode) is attached to the ferrule on the paintbrush and the positive lead (anode) is attached to the work piece. Again, rubber gloves must be used to avoid electric shock.






In the above photo, I’m anodizing the slots in a pocket clip using a small paintbrush. I created a “rainbow” effect by gradually slowing down each brush stroke. The following photo shows the results.






I carefully sanded the top surface of the pocket clip to remove any overruns, and cleaned it again using ammonia-based window cleaner. The next step involved reconnecting the power supply leads to the cathode strip (-) and the titanium wire hook (+), setting the voltage at 28VDC, and submerging the pocket clip in the electrolyte bath. The following photo shows the results.






Because the slots were anodized at a DC voltage setting greater than 28, the colors remained after anodizing the rest of the part at 28VDC.

The following photo shows the standard bath setup used to apply the blue color on this pocket clip.






The following is a good reference link to the process of anodizing titanium and other reactive metals:

http://www.reactivemetals.com/

General notes:

Anodizing titanium is a different process from anodizing aluminum. There are no dyes or acids used and, thus, the range of colors is limited. (For example: bright red or black cannot be achieved when anodizing titanium with the process described herein.)

Other differences between the processes used in anodizing titanium and aluminum include:

1. The surface of the titanium part is not hardened (like with TYPE 3 anodization of aluminum), and can be easily scratched.

2. A microscopically thin oxide layer that is refractive creates the color.

3. The color will dull from skin oils (or other dirt) during handling. Removing the skin oils with an ammonia-based cleaner, acetone, alcohol, etc can restore the color.


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## 65535 (Jan 26, 2010)

Hey Tom, good to see you over here.

Where did you source your power supply from? It sounds like a beast of a unit, far better than a Variac Rectifier and Caps.


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## souptree (Jan 26, 2010)

Great to see you here, Tom. Welcome to CPF! Fantastic tutorial, thank you!

There is a thread on anodizing Ti in the McGizmo subforum you may find worthy of a glance.

:thumbsup:


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## jch79 (Jan 26, 2010)

Tom,
Awesome tutorial! :twothumbs
Great to see you on CPF. I love admiring all of the amazing work on your website.
:thumbsup: john


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## Th232 (Jan 26, 2010)

Good to see you here as well Tom, nice tutorial.:thumbsup:

Now go on and post more of your stuff in the gadgetry section!


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## Tom Anderson (Jan 26, 2010)

65535 said:


> Hey Tom, good to see you over here.
> 
> Where did you source your power supply from? It sounds like a beast of a unit, far better than a Variac Rectifier and Caps.



I actually have several DC power supplies. The three in my "Tower of Power" cabinet are Sorensen brand. The unit shown on the top is solid state and a lot lighter than the DCR units below. All of them work very well - but I like the digital meters on the DCS150-7 unit. (Besides, it puts out 1Kw of power!  )









souptree said:


> Great to see you here, Tom. Welcome to CPF! Fantastic tutorial, thank you!
> 
> 
> There is a thread on anodizing Ti in the McGizmo subforum you may find worthy of a glance.
> ...



I don't know why I didn't register here before. :thinking:

I'll have to check out that thread on anodizing. Thanks!



jch79 said:


> Tom,
> Awesome tutorial! :twothumbs
> Great to see you on CPF. I love admiring all of the amazing work on your website.
> :thumbsup: john



Thank you, John! There's a lot of great information and cool people here on CPF!  



Th232 said:


> Good to see you here as well Tom, nice tutorial.:thumbsup:
> 
> Now go on and post more of your stuff in the gadgetry section!



I don't want to come on too strong and risk irking the moderators. After all, they were kind enough to let me in and I'm very thankful for that. 

If you see anything of mine you'd like to talk about - or if you just want to know how I build and finish my titanium gizmos - I'll be happy to answer your questions.


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## 65535 (Jan 26, 2010)

So Tom, the unit will only provide 7A at any voltage though correct? Which is 0-1Kw but say at 50V only 0-350w depending on current selection?


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## Tom Anderson (Jan 26, 2010)

That's right. I can dial in up to 7 amps of power throughout the 0-150VDC range.

The larger the amperage, the larger the workpiece can be.

Most of the anodization I do is actually under 105VDC.


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## cmacclel (Jan 26, 2010)

I have played with anodizing titanium and have never seen my power supply go over maybe 0.1 amps. Why do you need a 7 amp supply? I anodized a hole light and the amps draw was almost nothing.


Excellent work BTW!

Mac


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## darkzero (Jan 26, 2010)

Nice to see you here Tom! Your work is amazing & I envy all of it. Love your shop too & your Ti stock/collection is amazing! So far you have the biggest piece of titanium I have ever seen on a mid size lathe! :twothumbs


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## vestureofblood (Jan 26, 2010)

Very very nice work. Thanks for the tutorial as well.


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## Tom Anderson (Jan 27, 2010)

cmacclel said:


> I have played with anodizing titanium and have never seen my power supply go over maybe 0.1 amps. Why do you need a 7 amp supply? I anodized a hole light and the amps draw was almost nothing.
> 
> 
> Excellent work BTW!
> ...



I also have an Agilent 1/4amp DC power supply that I bought before getting my Sorensen units.

With the more powerful supplies, you can anodize much bigger pieces. 



darkzero said:


> Nice to see you here Tom! Your work is amazing & I envy all of it. Love your shop too & your Ti stock/collection is amazing! So far you have the biggest piece of titanium I have ever seen on a mid size lathe! :twothumbs



Thanks! That 37# hunk of 6AL4V was the biggest piece of titanium I've ever turned. 










vestureofblood said:


> Very very nice work. Thanks for the tutorial as well.



Thank you!


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## cmacclel (Jan 27, 2010)

Tom Anderson said:


> With the more powerful supplies, you can anodize much bigger pieces.



I have a nice Lambda 100v 10amp supply 


Where are the pictures of your shop?? That is a nice piece of Ti you got there!!! what where you making??


Mac


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## souptree (Jan 27, 2010)

That is freakin' preposterous. :twothumbs :bow:

I thought 6Al4V stock over 2" was reserved for the nuke industry. Pulling strings, Tom?



Tom Anderson said:


> Thanks! That 37# hunk of 6AL4V was the biggest piece of titanium I've ever turned.


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## Dan FO (Jan 27, 2010)

Welcome Tom, great to see you here!  You are a true asset to any forum and your products are above and beyond.


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## Tom Anderson (Jan 27, 2010)

cmacclel said:


> I have a nice Lambda 100v 10amp supply
> 
> 
> Where are the pictures of your shop?? That is a nice piece of Ti you got there!!! what where you making??
> ...



I'll post pictures of the rest of my shop equipment later - probably in a new thread. 

I just cleaned the big titanium bar up for now. I have a project in mind, but I'd rather not say what it is until I know everything will work out the way I want it to. There's still some Engineering and tool requisitions to do. :thinking:

Too many projects. Not enough hours in the day. 



souptree said:


> That is freakin' preposterous. :twothumbs :bow:
> 
> I thought 6Al4V stock over 2" was reserved for the nuke industry. Pulling strings, Tom?




Although the acquisition of that titanium bar had nothing to do with it, I once built reactors for the US Navy. I also built Naval chillers, so I guess you could say I worked both the hot and the cold parts of the ships. 



Dan FO said:


> Welcome Tom, great to see you here!  You are a true asset to any forum and your products are above and beyond.



Thanks, Dan!


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## csshih (Jan 27, 2010)

hey Tom! glad to see you here... thought your name looked familiar, USN


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## Tom Anderson (Jan 27, 2010)

Hi, Craig! :wave:


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## wquiles (Jan 28, 2010)

Thanks for the nice tutorial :twothumbs



Tom Anderson said:


> Too many projects. Not enough hours in the day.


Yup, I think most of us have that as one (if not "the") biggest problems :mecry:

Will


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## Tom Anderson (Jan 28, 2010)

Glad you liked the tutorial, Will! :wave:


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## reptiles (Jan 30, 2010)

Hi Tom, Welcome to CPF. 

I admired your work for a long time. 

I was wondering if the type of Ti affects its ability to anodize? For example, CP vs. 6AL4V etc. 

Regards, 

Mark


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## Tom Anderson (Jan 30, 2010)

Hi, Mark!

I haven't noticed any differences in anodizing between the grades of titanium I normally use (6AL4V solid bar and 3AL2.5V tubing).


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## Dan FO (Jan 31, 2010)

Tom Anderson said:


> Hi, Mark!
> 
> I haven't noticed any differences in anodizing between the grades of titanium I normally use (6AL4V solid bar and 3AL2.5V tubing).



As far as working, do you see a difference in 6AL4V and 3AL2.5V. The reason I ask is that several of the foreign flashlights are made of 3AL2.5 V. Do the threads seem to be smoother on one vs the other?


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## Tom Anderson (Jan 31, 2010)

The only 3AL2.5V titanium I've used has been on projects not requiring threading. Someone else here might be able to shed some light on the subject.


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## PhotonFanatic (Jan 31, 2010)

Dan FO said:


> As far as working, do you see a difference in 6AL4V and 3AL2.5V. The reason I ask is that several of the foreign flashlights are made of 3AL2.5 V. Do the threads seem to be smoother on one vs the other?



I can't see any difference in the smoothness of the threads between the two alloys.


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## 65535 (Feb 2, 2010)

Dan FO said:


> As far as working, do you see a difference in 6AL4V and 3AL2.5V. The reason I ask is that several of the foreign flashlights are made of 3AL2.5 V. Do the threads seem to be smoother on one vs the other?


 In most cases I imagine it;s just lower QC and tolerances on overseas production as well as worn tooling and machines that produce those results.


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## tino_ale (Feb 3, 2010)

Fantastic tutorial, thanks for sharing.

What I don't understand is why you recommend a 7 amps power supply for anodizing knife parts? Looks like Mac is reading around 0.1A for a flashlight, which I assume is comparable in size to a knife?

Are your knives huge? Coz I know Mac's flashlights are not tiny usually lovecpf

Also I don't see the risk of shorting the anode with the cathode, assuming your PS has a short-circuit protection, nothing dramatic should happen. Only as much current as you set on the PS will flow


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## Tom Anderson (Feb 3, 2010)

I've anodized much more than knife parts in the last 14 years. 

I'm not saying everyone _needs_ a 7 amp power supply. It's just what I use.

My little HP/Agilent power supply won't even start to color the bigger parts I anodize.

You guys know a lot more about electronics than me, though.


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## cmacclel (Feb 3, 2010)

How did you drill a hole for the live center in that nice chunk of ti?

Mac


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## gadget_lover (Feb 3, 2010)

Tom Anderson said:


> I've anodized much more than knife parts in the last 14 years.
> 
> I'm not saying everyone _needs_ a 7 amp power supply. It's just what I use.
> 
> ...



I'm not an expert, but as I understand it the choice of electrolyte (TSP in this case) and the distance between anode and cathode with have a great impact on the current that will flow at each voltage.

I think it's really neat that Tom has posted a chart for the colors that can be achieved with his particular setup at any given voltage.

Daniel


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## anarchy99 (Feb 4, 2010)

Hi Tom,

Thank you for sharing an information and how to do anodizing titanium.

I've confuse a bit and not quite clear about the spray glue that you use for multiple color, also type of brush that you use.

I buy a small paint brush, it's has a metal ferrule but it's now working as you do.

Please give me some advice how to do.

Thank you


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## Tom Anderson (Feb 4, 2010)

cmacclel said:


> How did you drill a hole for the live center in that nice chunk of ti
> 
> 
> Mac



I laid it out using a center head and drilled the hole with a hand drill.


gadget_lover said:


> I'm not an expert, but as I understand it the choice of electrolyte (TSP in this case) and the distance between anode and cathode with have a great impact on the current that will flow at each voltage.
> 
> I think it's really neat that Tom has posted a chart for the colors that can be achieved with his particular setup at any given voltage.
> 
> Daniel



Thanks, Daniel. This tutorial was actually written a while back in correspondence with a knife manufacturer. He wanted to make sure he could anodize several parts at a time. I should have prefaced my first post to indicate that, but forgot about it. (It's tough getting old!  )



anarchy99 said:


> Hi Tom,
> 
> Thank you for sharing an information and how to do anodizing titanium.
> 
> ...



The spray glue I use is 3M High-strength 90. You can remove it using mineral spirits after you're done anodizing.

I've been using a small sable hair brush with a steel ferrule. You need to have good contact with both leads - the positive lead attached to the part to be anodized and the negative lead attached to the metal ferrule on the brush. In comparison the the submerged method, it takes a while longer until the color appears.


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## PEU (Feb 5, 2010)

Tom, one question, I happen to have almost 5 meters of 21mm round TI bar and it would be nice to make a cane, not that I need one, but I always liked canes, why do you use tube for the cane? is just for the weight or there is another reason?


Pablo


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## Tom Anderson (Feb 6, 2010)

Depending on the diameter, titanium canes with solid shafts can get very heavy. (I made a few years ago.)


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## wykeite (Feb 8, 2010)

Tom, a couple of observations/questions.

I have anodized quite a few pieces in the past, I seem to get a better colour saturation on virgin bar as opposed to machined bar. I've tried many finishes, none quite come up to it. Any hints?

I've used a stainless tube for the cathode, is it time to get a large surface area piece of Ti to replace it? I use Ti wire to connect to the anode.

I find the colours that I acheive come at a slightly lower voltage than yours possibly because I use very dilute Sulphuric acid or occasionally bicarb.

My set up is a 0-40 regulated voltage supply with lead acid batteries in series when required. That beautiful green is elusive though.

That's a lovely workshop you've got there.

Jim


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## Tom Anderson (Feb 8, 2010)

Hi, Jim!

A number of folks have told me they get different results than mine, but I suppose it could be that it's due to the fact that they're using different equipment.

I'm not sure why a virgin bar would give better results than a machined bar. I usually use Scotchbrite® to polish the surface right before anodizing the part (cleaning it with Windex® immediately before it goes into the tank.)

Try using a piece of titanium as the cathode and see if that makes a difference.


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## wykeite (Feb 8, 2010)

Thanks Tom,

I've tried the Scotchbrite and always use a solvent cleaner. I'll try a titanium cathode, it's about all I haven't tried.

Made an anodiser once with a dimmer switch et al. Absolutely magnificent rainbow effect. Trouble was the spectacular sparks etc outside the tank made it a one off. Still to this day don't know what I did wrong.


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## Tom Anderson (Feb 8, 2010)

wykeite said:


> Made an anodiser once with a dimmer switch et al. Absolutely magnificent rainbow effect. Trouble was the spectacular sparks etc outside the tank made it a one off. Still to this day don't know what I did wrong.



Sounds like one of my electronics projects!


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## McGizmo (Feb 8, 2010)

It has been my experience that any metal in the circuit and exposed to the anodize bath that is not titanium will definitely effect the oxide growth on the titanium itself, significantly. You can get Ti welding wire and thin sheet stock to use. I also use some Ti tweezers for small parts.


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## wykeite (Feb 8, 2010)

Tom Anderson said:


> Sounds like one of my electronics projects!


 
Another mechanical guy playing with wiggly amps:twothumbs.



McGizmo said:


> It has been my experience that any metal in the circuit and exposed to the anodize bath that is not titanium will definitely effect the oxide growth on the titanium itself, significantly. You can get Ti welding wire and thin sheet stock to use. I also use some Ti tweezers for small parts.


 
All Ti play starts this week, I'll let you know what occurs:shrug:.


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## anarchy99 (Apr 3, 2010)

Hi Tom,

I just have time to finish my project and this is it.

Spyderco Chokwe Custom from Thailand.

Thank you so much for your sharing knowledge and technique. :twothumbs


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## tino_ale (May 14, 2013)

-moved to a more relevant thread-


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## precisionworks (May 15, 2013)

Absolutely stunning.


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