axehandle
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Replatinizing and platinizing Ti.
I'm looking for an electrochemical way of thickening the platinum layer on a platinized titanium mesh. I'm also looking for a way to
electrochemically platinize titanium from scratch. So far, my searches have turned out scratch, or been commercials for $10000 platinizing machines.
Any ideas?
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Turel
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Cleaning
Searching google yielded results similar to what you saw. One result I saw claimed that Titanium oxidizes rapidly forming TiO2 which impedes
platination electroplating. It was said that NaOH and HCl washes commonly used for steel are not suitable for Ti. Makes me wonder just how difficult
it is to electroplate Ti.
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axehandle
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I remember (could be a false memory) something about a layer of rhodium that had to be applied first.
But if they're _already_ platinized... I would think that it should be fairly easy. I just can't find any answers...
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chemoleo
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Hmm, to platinise a platinum electrode can't be done by chemical methods, simply because of equal electropositivity (--> same elements).
However, I am sure this could be done electrolytically, whereby the Pt electrode is the cathode, so that Pt(x+) is deposited there.
I should think most soluble Pt salts could be used.
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unionised
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This page gives a method for replatinizing electrodes (and, if anyone knows what the lead acetate is for, could they please let me know)
http://fire.fws.gov/ifcc/monitor/RefGuide/total_dissolved_so...
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axehandle
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Hmm thanks. I found that link myself when I tried to find a method, but found it vague, to say the least.
Chemeleo, I *think* your method would work, but I'm hesisant to try it unless I'm 100% it will work, given the price of platinum....
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chemoleo
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Hmm I honestly don't see why it shouldnt work. It works, for instance, with CuSO4 and Cu electrodes (by own experience).
So why not with Pt? It's not like it's a major breakthrough or anything, just normal plain electrochemistry?!?
I agree though, you haven't got much material to waste.
In that case, maybe it might be a nice idea to dissolve Pt (check references for that, for the best salt of this), and then plate it onto the Pt wire.
See if it changes texture (because it should providing Pt is deposited). Electrochemically of course.
You won't lose material at all as it is a contained system - a known amount of soluble Pt salt, and a known amount of Pt electrode. The Pt
won't just evaporate, either it sits on the electrode, or it remains in solution, unchanged. See what I mean?
Just 'sacrifice' a tenth of your Pt, and dissolve it in the necessary acids. Determine which compound salt is most suitable.
Then, do electrolysis, using Pt as a cathode.
If the Pt cathode changes in texture, you know Pt has deposited. If not, nothing is lost, it's still in solution, and you can use it for other
purposes...
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axehandle
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Excellent idea. I'll dissolve it in HCl using AC electrolysis, making hexachloroplatinic acid (is this the right name?), which I intended to make
anyways to platinize silica with for usage in a test of the contact method for making HNO3 at some later point.
If it leads to a complete fuckup, well, then all I have to do is sulk for a while.
[Edited on 2004-4-16 by axehandle]
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chemoleo
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Lol - you can't lose anything from this experiment. If it doesnt work (although I don't see a reason why it shouldn't), then you lost
nothing. All the reagents are still there.
Nonetheless - I haven't checked, but I doubt Pt would dissolve in simple HCl - I would have thought it needs at least HCl/HNO3 (aqua regia). It
needs the oxidising power, which HCl doesnt have!
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axehandle
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It's supposed to work sans the nitric if you use AC. I think it was Organikum that told me after reading about it in some German university
paper.
Edit: I suppose I could melt a pint of Pt and dip the mesh in it a couple of times... 
[Edited on 2004-4-16 by axehandle]
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t_Pyro
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Sorry for playing spoilsport, but...
Hexa chloroplatinic acid has Pt in a positive oxiadtion state, but IIRC, it does not freely exist as platinum ions in solution. Also, Pt won't
dissolve in HCl alone. It dissolves in aqua regia due to the high oxidising power of NOCl formed in situ.
A compound which I came across, which IS used for electro-plating of platinum is diammine dinitrito platinum(II) : Pt(NH<sub>3</sub> <sub>2</sub>(NO<sub>2</sub><sub>2</sub>. More information on Pt plating here and here.
An interesting article to read would be patent number 6306277.
[Edited on 16-4-2004 by t_Pyro]
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unionised
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This page
http://66.102.11.104/search?q=cache:E_hnvGvXhxUJ:www.tps.com.au/handbooks/MICROCv1_01.PDF+platinising+platinum+lead&hl=en&ie=UTF-8
Gives more detailed information (right at the bottom).
Any soluble platinum compound that you happen to have about the place should do.
Chloroplatinic acid gives PtCl4 2- ions in solution, they still get reduced to the metal at the cathode.
I presume Axehandle is joking about dipping the electrode into a pint of molten platinum. We all know that the titanium would melt. 
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t_Pyro
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| Quote: | Originally posted by unionised
Chloroplatinic acid gives PtCl4 2- ions in solution, they still get reduced to the metal at the cathode. |
In that case, I guess the chloroplatinic acid method would be the easiest method after all.
I remember reading an article about how certain surfaces (including plastics!!) are metal-plated by exposing them to a cloud of the metal vapour,
allowing it to condense and form a uniform coating. I'm not sure exactly how it is done, but I remember it involves stringing some metal beads on
a heater wire, and passing a high current through the wire to instantly vapourize the beads. Perhaps this method (with some modifications) could also
be used. I'll scan the original article and post it if/when I can find it.
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axehandle
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| Quote: |
I presume Axehandle is joking about dipping the electrode into a pint of molten platinum. We all know that the titanium would melt.
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Yes, that's the primary reason. The secondary is that I only have half a pint, about 4kg, of pure Pt at home (and a friend has borrowed my 3000C
electrical tungsten filament melting oven).
| Quote: |
I remember reading an article about how certain surfaces (including plastics!!) are metal-plated by exposing them to a cloud of the metal vapour,
allowing it to condense and form a uniform coating. I'm not sure exactly how it is done, but I remember it involves stringing some metal beads on
a heater wire, and passing a high current through the wire to instantly vapourize the beads. Perhaps this method (with some modifications) could also
be used. I'll scan the original article and post it if/when I can find it.
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Electrical connectors are, or at least were, electroplated with gold by vapourising gold in a vaccuum, letting the gold condense on the substrate.
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Texium
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