# Anodizing Ti vs. Al



## Morelite (Mar 19, 2006)

If the two different metals are anodized with the same type weather it be type 1, 2, or HA is there a difference is the hardness of the coating. 
example; will the anodize on titanium be stronger than the anodize on aluminum?


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## Christoph (Mar 19, 2006)

Ti can be colored but it is not anodized.


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## bfg9000 (Mar 19, 2006)

But you can anodize titanium at home with a battery and some cola: http://www.popsci.com/popsci/how20/3f178ca927d05010vgnvcm1000004eecbccdrcrd.html

The resulting rutile coating is harder than cobalt but less than quartz.


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## bfg9000 (Mar 19, 2006)

BTW the hardest coating for titanium is nitriding, which results in a gold color (think edge retention for titanium nitride coated drill bits and knives). It is as hard as corundum and has no flaking issues since it is directly formed on the titanium.

Scattered crystals of corundum in a porous matrix (that can hold dye) are responsible for the hardness of HA3, while titanium nitride itself has a crystalline structure, being a ceramic.


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## McGizmo (Mar 19, 2006)

Both the anodize film of Ti and Al are primarily an oxide film of the metal itself. The film thickness on he Al is many magnitudes thicker than the fim thickness of oxide on Ti. I don't know how the hardness of the two compare but the substrate of Ti is harder than Al which is advantage Ti but the significant film thickness of Al oxide is advantage Al. Unless the Ti is anodized for color, scars and abraision through the Ti film will not be nearly as noticible as those in the Al film. Ti will heal with the formation of a new oxide layer almost immediately and once that layer is in place, the metal is inert to further corrosion or degradation to all but some nasty acids.


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## Morelite (Mar 19, 2006)

Thanx Don, That makes sense to me. I would probably never want to anodize Ti on an item that is likely to be subjected to wear and abrasion, it would be to hard to keep it looking like new. But I do like the colored Ti art pieces I have seen around. For a flashlight, I love the natural Ti Look and I'm eagerly awaiting the Ti PD (hint, hint). I will probably have to get two of them, My wife won't let me get one unless I get her one too. She has been trying very hard to commandeer my Nat PD.


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## wtraymond (Mar 19, 2006)

They often use titanium racks when anodizing aluminum as the oxide coating on the titanium conducts enough electricity that it doesn't need to be de-anodized before using it again. The aluminum racks gradually wear away after subsequent trips through the anodizing/de-anodizing process.


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## chesterqw (Mar 24, 2006)

i would like a Titanium nitride coated titanium light if i could afford one...(ok lets say in 5 years time) that would be cool and strong then ha3 coating!(and gold is a nice colour too)
or we can try someting powerful and mysterious : http://en.wikipedia.org/wiki/Plasma_electrolytic_oxidation


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## velmeran42 (Mar 30, 2006)

Just a quick chime in on Ti. I have a cheapo Ti ring that I anodized with around 45V DC and some Coke. I firescaled it when I was done by throwing it in the hot coals of my BBQ chimney while starting the coals. It stayed black for almost a year before it started wearing through. I've been meaning to redo my ring, but haven't gotten around to it. I'm thinking of making a quick AC/DC rectifier with some diodes and caps so I can get a thicker oxide layer next time, or maybe an arc welder....... Anyhow, I'm sure everyone knows to be careful with anything over 30V (or any voltage for that matter).


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## IsaacHayes (Mar 30, 2006)

velmeran42: when you say black, do you mean straight black like a black maglite, or more of a dark chrome? I love dark chrome color like polished hemotite, but have no idea how or if it can be done on metal?

Yeah, I think 40v is the threshold to go through skin, but I wouldn't mess wiht 30v trying to see if it won't!


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## velmeran42 (Mar 30, 2006)

It was initially like a black chrome, dark and shiny (except on the sandblasted section, which was still textured looking). I think I'll be re-doing the ring this week, time permitting, since it's worn back to the colored oxidized layer on the inside of the ring. I'll post pics if I do.


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## Morelite (Mar 31, 2006)

velmeran42 said:


> Just a quick chime in on Ti. I have a cheapo Ti ring that I anodized with around 45V DC and some Coke. I firescaled it when I was done by throwing it in the hot coals of my BBQ chimney while starting the coals. It stayed black for almost a year before it started wearing through. I've been meaning to redo my ring, but haven't gotten around to it. I'm thinking of making a quick AC/DC rectifier with some diodes and caps so I can get a thicker oxide layer next time, or maybe an arc welder....... Anyhow, I'm sure everyone knows to be careful with anything over 30V (or any voltage for that matter).


 
What color did it turn out with just the coke, before the firescaling?

Another question, Can Ti be heat treated to produce a color change without doing anything beside applying controled high heat?


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## Silviron (Mar 31, 2006)

Heat coloring titanium doesn't give as deep or vibrant colors that electrolytic anodizing does...

And for the best results in terms of colors and thickness of color layer, prior to anodizing you should etch the titanium with a mixture of hydrofluoric and nitric acids. Course, that hydrofluoric acid is hard to get and VERY nasty stuff. McGizmo or one of the other metal experts here knows of something that works as well and not so dangerous... I can't remember what it is, but maybe he / they will chime in.

I use a variac and a bridge rectifier for my anodizing power supply, and trisodium phosphate (TSP) for my electrolyte; With that setup, you can get just about any color imaginable on your Titanium (or niobium or tantalum.)

OR: Do a CPF search... A year or two ago there was a good discussion here on Ti anodizing.


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## velmeran42 (Apr 1, 2006)

Morelite said:


> What color did it turn out with just the coke, before the firescaling?


Ti cycles colors from light blue, dark blue, yellow, red, etc depending on the voltage applied. Don't recall the repeat spacing, since I only do it prior to firescaling.



Morelite said:


> Another question, Can Ti be heat treated to produce a color change without doing anything beside applying controled high heat?


Don't know, I only oxidize and firescale, as I learned from a body piercer of all people (they have Ti and niobium jewelry)


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## flash (May 4, 2006)

Just out of curiosity, what determines the thickness of the anodize coating? The time?


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