| Pages:
1
..
4
5
6 |
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
After a two-day run, today I emptied the cell.
The electrode has become bubbly: clearly, the platinum did NOT make a very good bond. Some areas are still connected, but the whole surface is not
covered.
I also prepared an anode at higher current density, finding deposition rate does not depend much on current density. The deposit is still black. It
also performed very poorly in mechanical terms, without even exposing it to anodic conditions. Attempts were made to passivate or anodize the exposed
areas, with no useful effect.
I tested it in a bromate cell: the areas of exposed titanium corroded rapidly, filling the cell with white hydrous muck. Titanium is listed as
incompatible with bromine, so this shouldn't come as much of a suprise. I recommend using graphite, solid platinum or a suitable oxide anode in a
bromate cell.
In contrast, the perchlorate cell's titanium substrate is in original condition, minus some flakes of platinum.
I have found that boiling sulfuric acid is somewhat capable of attacking titanium, producing a blue or purple corrosion product which washes off.
Boiling-hot 50% NaOH causes a slow darkening of the surface, which can be removed with 3M HCl. Fluoride is capable of etching the surface, and
elemental or anodic bromine is capable of heavy pitting. HCl(aq), Cl2 and anodic perchlorate conditions are all inert.
Presumably, I need a combination of one of these corrosive processes to expose titanium, with a levelling agent in the bath to produce bright
platinum. I don't know why I'm not getting the bright deposit I did originally.
Edit: Oh, and the cell liquor. I weighed 103.5 g solution and added concentrated KCl solution to it, immediately producing a thick, chalky white
precipitate. I will seperate it from KClO3 and determine the concentration gravimetrically, calculate yield, then add a nearly stoichiometric amount
of boiling, concentrated KClO3 solution to precipitate KClO4, leaving NaClO3 in solution.
Tim
[Edited on 1-1-2008 by 12AX7]
|
|
|
chloric1
International Hazard
Posts: 1143
Registered: 8-10-2003
Location: GroupVII of the periodic table
Member Is Offline
Mood: Stoichiometrically Balanced
|
|
| Quote: | Originally posted by 12AX7
I recommend using graphite, solid platinum or a suitable oxide anode in a bromate cell.
Tim
[Edited on 1-1-2008 by 12AX7] |
That reminds me, remember reading in US339996 that they recommend not using cobalt bromide as an electrolyte to deposit cobalt oxide anodically. It
was something to do with the voltage to break down the bromide being less than 0.7 Volts not allowing the oxide to form. Merk lists Co3O4 as
dissolving in HCl with evolution of chlorine. The bromide ion may reduce it to a point that it will dissolve or no longer function.
Since this oxide will be the backbone of our anode design, I am not sure if it can be used for bromate synthesis. Any thoughts on this?
Fellow molecular manipulator
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
Sorry to hear the Pt didn't stick. I know the feeling. I wonder if electrocleaning or hydriding of the titanium would've helped?
I was able to plate a thick, nice-looking layer of cobalt onto hydrided Ti, very successfully (it had to be sanded off), but I couldn't do anything
with cobalt oxide.
I still think anodically co-deposited Co3O4 and MnO2, followed by baking, is worth a shot, but I don't have a furnace yet, so I unfortunately won't be
able to try it in the near future.
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
I remember reading that platinum cannot be electroplated to titanium from aqueous solutions at all.
What I can say for sure is that platinum clad titanium electrodes are made by a molten Pt salt electrolysis at a temperature above 500°C where the
oxide layer on titanium is not stable.
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
I was able to plate cobalt onto Ti by hydriding it first...and patent #4127709 claims to accomplishe nickel plating on Ti, also by hydriding first.
|
|
|
Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
|
|
This is what you're referencing:
http://www.finishing.com/4400-4599/4497.shtml
That is ridiculously expensive, but it is a method.
I should like to correct garage chemist on that, it is indeed possible to plate Titanium in aqueous medium with platinum.
It is anode pretreatment that is absolutely essential!!
I sent Tim hydrazine sulfate too, because I remember reading a patent about electroless, jewelery-finish (therefore adherent) platinum plating done
hydrazine sulfate. Personally, I don't think he did sufficient etching and from what I've seen and experienced, Ti needs aggressive pretreatment. So
in addition to sanding, other chemical etches must be performed, and the anode-to-be kept under water all the time, only being exposed to air as it is
transferred to the plating vessel.
Additional references provided to me by a friend on another forum, who is a professional metal plater who also says it's quite possible.
http://www.finishing.com/243/65.shtml
http://www.finishing.com/134/56.shtml
http://www.hikifune.com/english/product/toku/ti.html
( a company that uses a proprietary method to platinize)
Example regimen for pretreatment courtesy of Dr. Trevor Crichton:
"Titanium can also be electrochemically processed by etching in a solution of:
NH4HF 10-40g/l
H2SO4 5%v/v
Temp 20C
Leave for 30 secs or more AFTER gassing starts.
The titanium is then activated in:
HF(40%) 50-70ml/l
HNO3 50-100ml/l
H2O2 100-200ml/l
Temp: RT
Time 5-10 secs
Once activated, the titanium can be strike plated with Woods Nickel. It is essential that NO RINSING takes place between the activation and strike
plating. I believe this was documented in Trans. IMF. 1966 p74 "
That is very much in line (as far as pretreatment goes) with what I remember reading. Hence the reasons I sent what I sent to Tim.
[Edited on 3-1-2008 by Fleaker]
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
Well I sanded my piece of Ti with 220 grit SiC paper, washed it with detergent solution, cathodized it for 10 minutes at about 50 mA/cm^2 in 10%
oxalic acid, and plated it with Co...and I challenge anybody to remove the Co.
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Hello,
The following was posted by DerAlte in another thread. I though I should cut and paste here for completeness.
Dann2
| Quote: | Originally posted by DerAlte
To the best of my knowledge, perchlorates CANNOT be produced by the electrolysis of chlorates using carbon as an anode.
I had two samples, produced in 1995. One, labeled Chlorate (call it ‘C’ for short) was produced by electrolysis of saturated NaCl using a carbon
anode. Part - the major part – was used by metathesis with KCl to produce KClO3.
The rest was then somewhat purified to get rid of as much NaCl as possible and subjected to further electrolysis, following a convincing sounding
procedure “guaranteed” to produce perchlorate (found somewhere on the WWW). I added KCl to the electrolyte at this point order to precipitate any
KClO4 so formed. I kept temperature much lower (by reducing current density and ohmic losses) than in the first case, since I assumed the process was
a purely electrochemical ion oxidation conversion, with a different cell configuration (wide anode/cathode separation). A precipitate was formed.
This was bottled as ‘KClO4 (impure)’ – call it sample ‘P’. The only use I ever made of this was to demonstrate a few pyrotechnical reactions
to my younger son. It seemed less reactive than the sample C.
When Dann called into question its composition, I sought methods available to me to determine this. I did not have conc. H2SO4 available nor Methylene
Blue.
Chlorates react with any strong acid to give either Cl2 or ClO2 or a mixture; perchlorates do not, due to the kinetic barrier which accounts for their
relatively poor oxidation performance, although the thermodynamics favor it over chlorates.
(1) A test of P with HCl gave off a gas that was either Cl2 or a mix with ClO2, by nose test. Conclusion: P contains Chlorate. This does not
definitively say it does not contain perchlorate, however.
(2) Saturated solutions were made of both samples and a drop placed on a microscope slide and allowed to evaporate slowly. Crystallization was
observed under X50 mag.
Result: C gave lozenge shaped crystals characteristic of KClO3, plus a few needles. Both of these forms are possible under the monoclinic
classification of KClO3, where sides may be unequal but parallel and only one angle is a right angle.
P also gave the same shapes in the main – only one crystal was orthorhombic, where all angles are right angles, but sides unequal (unlike cubic)
which is characteristic of KClO4. However, needles were also produced, and perchlorate can also be of the needle form (it is isomorphic with KMnO4,
which tends to make needles in my experience).
Conclusion: If there was any perchlorate in P, it was a small amount.
(3) 1.000 g (+- 0.005g) of each of C and P were dissolved in 33.3 mL (+-0.3mL) water at RT – both dissolved. This shows that less than 70% was
perchlorate. The solution was so chosen that pure chlorate would be just saturated at 0c. Both solutions were cooled for 3 hrs. in a water bath in a
refrigerator to slow the ice melting. One or two small crystals were then seen floating in C; none in P. The P solution was somewhat turbid at the
start and a fine white ppt. settled during cooling, but there was very little of it. Examination under magnification showed what looked like particles
of a fibre. Non –crystalline.
The conclusion from test 3, (solubility) indicates that not more than 0.25g in solution (<25%) could possibly be perchlorate. Taking account of the
common ion effect, even including activity coefficient (from CRC) reduces this to a maximum of 0.063 g (<6.3%).
Overall conclusion: if perchlorate was formed at all, it was probably less than 5%. I was merely oxidizing carbon! Moral: Don’t believe what you see
on the web, however convincing. And do some tests, always…
DerAlte
|
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
My Cells (plural)
Seems proper to put in here, as all three are running perchlorate at the moment.
Put together two new cells last night and tonight. They both consist of 4" steel pipe, well rusted on the inside (and sulfury -- pew!). A 1/8" steel
plate was hacksawed to shape (I need a bandsaw...) and welded on. The first one had a pinhole leak after the first pass, while the second was
perfectly sealed as welded.
The first one seems to be hogging current; the large cell has cooled down substantially, and is probably running much less current now. The ballast
is reading near 1V of drop (corresponding to about 30A total consumption), probably a good point to cut it in half and see if I get more current
flowing through them all.
I'll probably set one to perchlorate duty, and the remaining two for chlorate production. That should about balance out.
We'll see where I get by june! 
Tim
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
Your cells are running your Pt plated Ti Anode, Tim?
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Yes, all three of them. At least, what area of the anode *is* plated...
Tim
|
|
|
MadHatter
International Hazard
Posts: 1339
Registered: 9-7-2004
Location: Maine
Member Is Offline
Mood: Enjoying retirement
|
|
Intended Use Form
I'm still working with PbO2 anodes. Never can seem to make one that doesn't want to
disintegrate in the cell.
A general chemical supplier that I've done business with now wants the intended use form
for KClO3, KClO4, NH4ClO4, and NH4NO3. Now more reason for me to make my own chemicals.
It appears that the CPSC's bullshit is scaring more and more suppliers.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
|
|
|
hector2000
Hazard to Others
Posts: 127
Registered: 22-8-2006
Member Is Offline
Mood: Cool
|
|
There is PbO2 sheet in the car battery May we use of it(for anode)?
Chemistry=Chem+ is+ Try
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Read the archives, that PbO2 is not nearly robust enough.
Tim
|
|
|
Lewis
Harmless
Posts: 8
Registered: 6-7-2008
Member Is Offline
Mood: Excited
|
|
I'm not sure if this has been covered, but there are sources of MMO coated Ti anodes out there. There were a few (overpriced) ones on
eBay, a supplier in India, and a pyrotechnical company in the States. For everyone looking to go this route (and I would highly recommend it), PM me
for details.
These electrodes are stellar choices any way you swing it. They will apparently show no sign of wear after even tens of years if treated well. I can
assure you mine have served me well since I purchased them.
As far as what the MMO coating is, I actually have no idea. I didn't inquire, but they sure as hell work wonders on chlorate/perchlorate cells.
|
|
|
Xenoid
National Hazard
Posts: 775
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline
Mood: Comfortably Numb
|
|
| Quote: | Originally posted by Lewis
I'm not sure if this has been covered, but there are sources of MMO coated Ti anodes out there. |
Hmmm...! Yes it has been covered. See the various anode and chlorate/perchlorate threads in Technochemistry. As far as I'm concerned, the ready
availability of exotic anodes has just about sounded the death knell for home anode making, other than perhaps PbO2 coated Ti.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Here's an interesting coating scheme
http://www.youtube.com/watch?v=cBpcF8ipqq0&feature=relat...
|
|
|
chloric1
International Hazard
Posts: 1143
Registered: 8-10-2003
Location: GroupVII of the periodic table
Member Is Offline
Mood: Stoichiometrically Balanced
|
|
Damn it Rosco I got a chubby. Can't concentrate on chemistry....be back later
Fellow molecular manipulator
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Perchlorate from MMO?
| Quote: | Originally posted by Lewis
.....................
As far as what the MMO coating is, I actually have no idea. I didn't inquire, but they sure as hell work wonders on chlorate/perchlorate cells.
|
Hello Lewis,
Have you actually made Perchlorate with the MMO?
Have you started with Sodium Chlorate (pure or close to pure) or with Sodium Chloride.
How do you purify the Perchlorate (if you do).
All and every detail appreciated.
Cheers,
Dann2
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
| Quote: | Originally posted by chloric1
Damn it Rosco I got a chubby. Can't concentrate on chemistry....be back later |
 Yeah,
that is an example of spray pyrolysis gold coating if I ever saw one.....or maybe she just melted and fused all her jewelry there in a transient
moment of sultriness There's no hitting that lady with a snowball, as it would
simply flash to steam in midflight a foot away from impact
kind of like the comet over Tonguska
Here's a clip of an earlier appearance.
http://www.youtube.com/watch?v=TxXPDvs4pDY
Please indulge my off topicness here for art's sake.
|
|
|
| Pages:
1
..
4
5
6 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
