Somewhat silly idea, but would it be possible to microwave-anodize titanium?

H

_habit_

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Oct 14, 2006
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I was just watching Mythbusters and they were explaining how a microwave "cooks" food and why aluminum catches on fire inside the microwave, and the thought came to mind of titanium anodization, and the possibility of doing it that way... is it possible?

:confused::confused::confused:
 
We could ask STR to try it, surely he has a little bit of scrap Ti laying around. The question is whether he has a spare microwave laying around.
 
Before plugging in that microwave, might I suggest a 100' cord to use, also need remote switching. Just in case.

Good Luck on trying something new. :D :D :D
 
_habit_ said:
I was just watching Mythbusters and they were explaining how a microwave "cooks" food and why aluminum catches on fire inside the microwave, and the thought came to mind of titanium anodization, and the possibility of doing it that way... is it possible?

:confused::confused::confused:
Click to expand...

No, it is not possible. Titanium and Microwave make bad Juju.

For a somewhat more technical explanation, look here:

http://www.gallawa.com/microtech/metal_arc.html
 
That explanation didn't necessarily say that it wouldn't work, just that it would do very bad things to your microwave.

What if you had the Ti in a bath?
 
FlyingMuskrat said:
That explanation didn't necessarily say that it wouldn't work, just that it would do very bad things to your microwave.

What if you had the Ti in a bath?
Click to expand...

If I remember correctly, anodizing Ti takes a DC voltage. Any induced current from the microwaves would be AC.
 
Alright, I've been trying to find information regarding the DC voltage and AC voltage stuff, and I found this:

http://users.lmi.net/drewid/PWR_reactive_metals.html

Taken from that site:

Conveniently, if one uses a common variable transformer (variac), with rectifying diodes and a large filter capacitor, one gets that voltage range with household current. Note, however, that variacs are not an isolated transformer type, and one should never use one simply plugged into the wall. Use it with an isolation transformer as well, for safety. Even with this, the process requires careful attention to safety, since one is dealing with potentially lethal voltages. I'll also note that AC can be used as well, with anodic coloring taking place during only one-half cycle. However, this wastes current, and generates heat, which can create burning effects on the metal. Often, AC-developed colors are not quite as good as DC-produced ones. Since diodes are cheap enough, rectify the current for best results.
 
habit, thanks for the link. Answered a lot of my questions on how to get different colors on one piece.
 
pkdmslf said:
habit, thanks for the link. Answered a lot of my questions on how to get different colors on one piece.
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Umm, no problem :cool:

Hope that works out for you :)



From my earlier post:

I'll also note that AC can be used as well, with anodic coloring taking place during only one-half cycle. However, this wastes current, and generates heat, which can create burning effects on the metal.

Since the AC waves (we believe it's AC) of the microwave would be constantly moving (or so my mind tells me), I should think it would be able to avoid burning effects.

Maybe we can get some experts back in here... knarfeng, where'd you go?

T. Erdelyi said:
Can't ya change the color of Ti with a torch?
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I've heard that before, and that sort of ties in with microwave heating like flame heating, but with the torch you're getting actual heat (and possible chemical reaction with the flames?), with microwaving it's essentially making the molecules and stuff move around at a very high speed, which causes friction to heat it (or so I understand from Jamie, Adam, and wikipedia)... I wish I had some Ti laying around, I'd try this myself (outside, of course).
 
T. Erdelyi said:
Can't ya change the color of Ti with a torch?
Click to expand...

R. Crumb !?!!!???

What a cool animation!

I have that, but in the strip form, IIRC in a Furry Freak Brothers.

Hell, I'm 58 and don't remember the late '60's till 1976 or so very well.

But if you wanna, you can bleed on me.

Rob
 
(Sorry folks, I'm on west coast time and I work late.)

Guys, I don't think there are any experts when it comes to anodizing with microwaves, cause nobody does it. I'm afraid you're stuck with a materials engineer who studied electro chem in college and who fooled around with microwaves and their reactions with materials for a spell. Don't ask.

There is a rather large difference in the frequencies. 60 Hz for household current vs 2.4 GHz (2,400,000,000 Hz) for microwave radiation. This makes a big difference in what can happen.

When you Anodize, you are depending on OH- ions (hydroxyl ions) to migrate to the surface of the Ti then be reduced by the positively charged Ti, forming water and TiO2. With a frequency of 60 hz, you have a positively charged surface for 1/60 seconds. That gives time for the hydroxyl ions to migrate to the surface of the Ti and react. The reaction is one way, so when the Ti becomes negative, the oxide layer remains. It could work.

With a frequency of 2.4Ghz the surface changes polarity every 1/2.4x10^9 seconds. the polarity would shift so fast that IMO the hydroxyl ions would not have time to migrate to the surface and react. The limiting factor would be hydroxyl migration rates rather than reaction rates. I got no data to prove it, Might get it if I worked a few hours in a university research library to look up anion migration rates in solution.

IMO it ain't a happening thing.



In edit I removed these statements because I forgot a conversion factor and the numbers were bogus. Sorry, I was moving too fast.
(Moreover, the wavelength of a 60Hz wave is a couple of miles in length. That means the entire piece of metal will be positive during that time period. ) (And the wavelength is about 1/2inch. That means that If you wanted to anodize a 3" piece of ti, the enitire piece of Ti would not be positive at once. And action. )
 
I would be inclined to agree with knarfeng, his theory makes perfect sense, at that kind of frequency the molecules and ions vibrate at 2.4GHz and have little time to migrate in such a high on off cycle.
 
65535 said:
I would be inclined to agree with knarfeng, his theory makes perfect sense, at that kind of frequency the molecules and ions vibrate at 2.4GHz and have little time to migrate in such a high on off cycle.
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What he said does... uhh, make sense (*is clueless on these things*)... would putting the microwave on different power settings change that 2.4 GHz?
 
_habit_ said:
What he said does... uhh, make sense (*is clueless on these things*)... would putting the microwave on different power settings change that 2.4 GHz?
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No, 2.4 GHz is the frequency that has the most effect on water molecules. (Microwave ovens work by heating water molecules in whatever you are heating.) When you change the power setting, you are actually changing the % of time that the microwave generator is on. Sometimes you can hear it kick on and off.

Thought of another issue. It takes a pretty good voltage to anodize titanium. When EM waves hit metal, most of the energy is reflected rather than absorbed. Most of the microwave energy is going to be reflected from the Ti into the solution. I don't think any induced voltage in the Ti is going to be strong enough to cause the reaction, even if the frequency were 60 hz. That guy who said you could anodize with AC was attaching an AC cord straight to the Ti. So he didn't have that problem.
 
I don't clame to be an EE, and this might just prove that, but AC voltage alternates poles sort off, by that I mean the electrons vibrate as opposed to a jumping motion between metal or conductive atoms, so high current AC would enduce a DC field? I would imagine that the DC field would be in some way related to the frequency of the AC, but to digress, don't stick Ti in the microwave.
 
it is the heat from the dc current that causes the outer layer of the Ti to anodize, change color.. you can get very nice results with a car battery and coke..don't like it you can just scotchbrite it off and try again.. not very durable actully it rubs right off if its not sealed over with like laquer..o and to the guy that wants to try the microwave on Ti ...lol.... make sure you have the camera runnin, my bet is you will at least get some decent sparks before it smokes....keep us posted
 
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