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Author: Subject: Cobalt Oxide Anodes
dann2
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[*] posted on 11-12-2007 at 16:37


Hello,

That's the problem with anodes. Making them (let they be good or bad) takes a relatively short space of time, testing takes months.
I have just completed two anodes. They each received 7 coats. (12 coats is for the hardened brigade only). One solution contained 2.5 moles Co(NO3)2 6H2O per liter,
15.5grams in 21cc solution.
The other anode was made with solution that contained 4.4 moles of Co(NO3)2:6H2O per liter (181grams in 143cc solution).
7 coats, 7 bakes at 380/400C for 10 minutes per bake. The anodes were given a final one hour bake at 390c.
The Ti substrate was etched in HCl for a few hours but they were washed and left in the atmosphere for about 16 hours before coating. (My solution was not ready, roll eyes icon here).

DTO in Perchlorate cell still going ok. I am going to leave it there to see what level it will drop the Chlorate down too.

Some patents I have not seen here (I think) are:
3706644 Regeneration of Spinel Electrodes (may be interesting, have not read).
3773555 is interesting. It shows you how to plate on a controlled TiO2 coat onto Ti using Sulphuric acid. May be useful.





Regarding hair styles:
The 3 hair styles of Man are:
1: Parted
2: Unparted
3: Departed


Dann2

[Edited on 12-12-2007 by dann2]
Second edit changed Carbonate to Nitrate

[Edited on 12-12-2007 by dann2]
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Twospoons
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[*] posted on 11-12-2007 at 16:56


@Xenoid: the way to attack epoxy is to get it nice and hot with your heat gun - this will soften it to a jellyish consistancy, which can then be easily dug out with a screw driver. I've used this trick to "un-pot" high voltage transformers (as used in electric fences).

Beautiful looking anode, btw!




Helicopter: "helico" -> spiral, "pter" -> with wings
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Xenoid
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[*] posted on 11-12-2007 at 17:00


Quote:
Originally posted by dann2
One solution contained 2.5 moles CoCO3 6H2O per liter,
15.5grams in 21cc solution.
The other anode was made with solution that contained 4.4 moles of CoCo3:6H2O per liter (181grams in 143cc solution).


Eh!..what... Is that Co nitrate or Co carbonate.... an inauspicious start...:o

The 4 coat anode in the chlorate is still OK after 5 days, the electrical parameters are still the same as when it started. The anode is definately eroding though, there are some thin areas, and there is now more black gunk floating around. I think it may only last for a few more days!

What is really needed is a set up for doing multiple anodes, say 6 at a time. I'm still looking at toaster ovens in this regard. I've had two over 300 oC. without adding extra elements, so it looks promising!
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[*] posted on 11-12-2007 at 17:06


Quote:
Originally posted by Twospoons
@Xenoid: the way to attack epoxy is to get it nice and hot with your heat gun - this will soften it to a jellyish consistancy, which can then be easily dug out with a screw driver. I've used this trick to "un-pot" high voltage transformers (as used in electric fences).

Beautiful looking anode, btw!


Yeah! I was thinking of getting a gas burner to it, and burning it off, but the smell is awfull. This epoxy is really hard, it's like porcelain, I've never seen anything like it before. I'll give the hot air a go!
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Xenoid
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[*] posted on 11-12-2007 at 18:17


Thanks 'spoons, I've finally got them apart. The epoxy never got to a "jellyish" state, it softened slightly, and then went a bit crumbly. I'm glad it wasn't a transformer I was removing, I had to apply a lot of heat!

Here's the separated electrodes, I will leave them like this until I come up with a cell design, at least each individual electrode can now be cut off, and have its own reasonably long, bent over attachment tag!

ChlorinatorElectrodes.jpg - 19kB
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dann2
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[*] posted on 11-12-2007 at 21:10


Hello,

That should be Nitrate, I edited the post.

@ Not_important.
If I was to fuze Sodium Carbonate with my Zr Oxide what ratio should I use?
Will I be able to fuze in a test tube is it more a job for a crucible or perhaps a stainless steel bowl (handiest for me).

@Xenoid. Is there still an MMO coating on the Ti electrodes do you think. It was a damm good find IMHO.

What is the suituation regarding Co contamination in (Per)Chlorate for pyrotechnics? Is there as safety issue.

Cheers

Dann2
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Xenoid
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[*] posted on 11-12-2007 at 21:30


Quote:
Originally posted by dann2
@Xenoid. Is there still an MMO coating on the Ti electrodes do you think. It was a damm good find IMHO.


Yeah, I mentioned earlier, the two outside electrodes have 100% on their outside surfaces, because they would never have taken part in the electrolysis process. There is some coat on the others, not sure how much, I will experiment!
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Rosco Bodine
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[*] posted on 11-12-2007 at 21:42


Monometal Cobalt spinel is not likely to be the *complete*
solution by itself *alone* , either as the ultimate interface material or as an operable working anode coating .

However , because cobalt spinel is so promising by itself , it is probably stirring up some exaggerated hopes concerning what it can do , beyond what it is actually very good at doing , which is producing highly conductive interfaces .

More reasonably cobalt spinel should be regarded as an exceptional component in a larger scheme where it
simplifies things and improves performance . It is not
a complete solution itself alone , but only a principal
ingredient in a greater scheme which is a synergistic system .

If you like what you are seeing with plain cobalt nitrate
baked onto etched and/or hydrided titanium , then
try a 7:3 molar mixture of cobalt nitrate with nickel nitrate ,
and you are probably going to like the result of that *mixture* even better .

http://www.sciencemadness.org/talk/viewthread.php?goto=lastp...

What should happen at the interface is a 40% reduction
in voltage for the same current density , and a 335% increase in longevity , for the 7:3 bimetal spinel as compared with the monometal spinel "control anode" ,
at least on a non-hydrided substrate . The above linked
paper attributed this in part to a greater suppression of
the growth of the TiO2 during baking of the interface layer
so the effect may not be so immediately evident in the case of a TiH2 substrate pretreatment . However , the
one thing it does suggest is a lower porosity and a higher
chemical resistance for the bimetal spinel , irregardless
of the substrate pretreatment .

Applying simply one or two coats of the spinel accomplishes the task of producing a highly conductive interface , which is arguably better than anything even
Ruthenium can provide in a "chlorides precursor" scheme
where the substrate is attacked , with or without Tin Oxide
and with or without Antimony adding more complexity .

You see , having a highly conductive and stable *spinel* interface on the Ti substrate dispenses with the complications presented by chlorides *entirely* ,
and whatever coating and layering schemes and chemistry
may be contemplated , can very likely be applied subsequently , so long as it doesn't disrupt the excellent
interface which has been achieved by the spinel .

This is like a starting point and foundation sort of interface
which can be a standard surface preparation for any
wearing anode coatings of any sort which may be wished to be applied on top of and encasing that spinel interface .

So in that much , no , cobalt spinel is *not* some sort of
"holy grail" anode coating , but it is more like something
of a holy grail substrate interface component at the very least , and depending upon the possible catalytic properties which some spinels might have with regards to
perchlorate production , perhaps then it might have that greater status , but unlikely to be so for the monometal
cobalt spinel . Even the Dow patents are clear about this . So there is definitely something of value here ,
but certainly cobalt spinel alone is not the whole story
or the whole perchlorate anode solution by itself .
But as a component , enhanced by mixture with other things , it could be a major *part* of a reasonably permanent anode . But barring some miracle that
a hydrided substrate has somehow transformed the
monometal spinel into a permanent anode when
some magic number of coats has been applied , then
it should be expected that this coating too will erode
at some observable rate for the monometal cobalt spinel "control anode" . This "control anode" is not
the end product "perchlorate anode" and should not
be expected to be , even though it probably can make
perchlorate and last for awhile , however long that may
be .

In all likelihood an SnO2 layer is still going to be needed
only now it shouldn't have to be used as the first interface layer , nor should it necessarily require antimony at all ,
nor should it require chlorides based precursors although
they may be intermediates if solder is the raw material .
One or two coats of the Sn++++ / Sn++ polymer , even completely *absent* the Sb component , or any other of the hydro-gel Sn related materials , but probably better the nitrate or ammonum stannate materials , should work just fine as a dip and bake to seal the porosity and lock down the spinel interface. It would seem possible that even precipitated SnO2 or its hydrates could be used
as a modifier oxide also in mixture with the nitrate spinel precursors .

@Xenoid

What alloy of Ti rod are you using for your experiments ?

[Edited on 12-12-2007 by Rosco Bodine]
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[*] posted on 12-12-2007 at 10:24
Sure isn't a holy grail...


I put my beautiful, smooooth, shiny and HARD anode with 12 coats in a perchlorate cell! It has been running for 15 hours now. A lot of black material has come off, and a thin patch has appeared.... :(

This cell initially ran at 3.7 volts and 1.12 Amps (50mA/cm^2) and seemed to produce a lot of bubbles and ozone! The voltage has now dropped to 3.6 volts, (at 1.12 Amps) it is only producing a thin stream of small bubbles, so it looks like it is making perchlorate. I am very disappointed in the way plain Co oxide is performing (lasting) in a perchlorate cell, although it does seem to be making the right stuff! Perhaps I rubbed off too much oxide, with my vigourous polishing between coats!

The 4 coat anode in the chlorate cell is still going well, although the current has dropped slightly ( 1.87 --->1.84 Amps). I feel the "end is nigh" for this brave little performer, and it's downhill rapidly from herein!
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Rosco Bodine
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[*] posted on 12-12-2007 at 10:35


No real surprise there :D

Cobalt spinel has never been purported nor advertised
as being a working anode coating . It is an interface
material , a TiO2 dielectric nullifier :D , a rectifying junction
discombobulation reagent :D , anodic current facilitator ,
as opposed to an irish tater .:o:D ;):P

Sooooo what alloy Ti rod is being used for your redundant proof of this ?
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[*] posted on 12-12-2007 at 10:48


Quote:
Originally posted by Rosco Bodine
@Xenoid

What alloy of Ti rod are you using for your experiments ?



I wouldn't have a clue, I bought it from some guy on the local trade site. He owns a sports store, so he may have been importing Ti products for bikes, experimental fishing rods, etc. He's a bit paranoid and wont tell me anything.

I already answered this, but forgot to post it, sorry....:)
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Rosco Bodine
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[*] posted on 12-12-2007 at 11:06


It's probably Ti-6Al-4V which is pretty much the most common alloy from all indications .

I sure hope that the enthusiasm for the Co related
technology isn't squashed by the realization it is
what it is and is good for what it is good for ,
useful as an interface and a system component .

I think there has been a bit of overexcitement about
the potential for Co spinel which has to be put in perspective in order to make practical use of it ,
with respect to its properties and limitations .
What it does do , it does very well .
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[*] posted on 12-12-2007 at 12:12


Quote:
Originally posted by Rosco Bodine
It's probably Ti-6Al-4V which is pretty much the most common alloy from all indications .

I sure hope that the enthusiasm for the Co related
technology isn't squashed by the realization it is
what it is and is good for what it is good for ,
useful as an interface and a system component .



I guess that is 6% Al and 4% V, what is the composition of electrode Ti, any difference! I gather Niobium and Ti/Nb are in use!

Well I still have plenty of enthusiasm...:D

These have been my most successful atempts yet! We are just scratching the surface (no pun intended). I still have heaps of things I want to try, I am just getting some "exotic" nitrates together first. I think it is important to get the basic techniques correct first! For, example my first coat, always looks crappy, and this is the most important one. It is probably easier to see defects, than with later coats which are over black oxide. It may just be useful to try a series of tests (using different conditions) with single coats., to see which performs best.
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[*] posted on 12-12-2007 at 12:42


When I get some MnSO4, I intend to try anodic electrodeposition of Mn-Co-O (as per the paper I uploaded) followed by some kind of heat treatment.

I'm told by one of the authors of one of the papers that Co3O4 doesn't stick very well but it's better when co-deposited with MnO2.

Another thing to try of course is TiO2 powder dispersed in the Co(NO3)2 solution...analogous to what Beer did.

If neither of these things work then I'll probably give up on cobalt myself.

[Edited on by jpsmith123]
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dann2
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[*] posted on 12-12-2007 at 12:58


Hello,


Quote:
Originally posted by Rosco Bodine
No real surprise there :D

Cobalt spinel has never been purported nor advertised
as being a working anode coating . It is an interface
material , a TiO2 dielectric nullifier :D , a rectifying junction
discombobulation reagent :D , anodic current facilitator ,
as opposed to an irish tater .:o:D ;):P

Sooooo what alloy Ti rod is being used for your redundant proof of this ?


Regarding the Discombobulator, my Uncle used to use one of these very useful devices but the wheel eventually fell off it.

The patent have shown (pure) Co Oxide (making Chlorine anyways) to have worked for 250+ days continous with only a small rise in voltage. I call that success. They were not making Perchlorate though. Perhpas it is much 'easier ' on an anode making Chlorine in a controlled Chlorine cell as opposed to making Chlorate in a non controlled cell (High pH). None of the Co Oxide patents have used the Co Oxide to make Chlorate (in a controlled cell or other wise) that I am aware of.
Some of the patents have sang the praised of Zr in conjunction with Co in the spinel but the examples at the back of same did not show a Zr containing spinel doing anything out of the ordinary that I could see.
The patents are obsessed with voltage accross cell = power used. This is not so important to us. We want a long lasting anode, a volt or so is not a problem.

Zr is the answer I tell you....

Dann2
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Rosco Bodine
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[*] posted on 12-12-2007 at 13:17


Quote:
Originally posted by jpsmith123
When I get some MnSO4, I intend to try anodic electrodeposition of Mn-Co-O (as per the paper I uploaded) followed by some kind of heat treatment.

I'm told by one of the authors of one of the papers that Co3O4 doesn't stick very well but it's better when co-deposited with MnO2.


Adhesion isn't the problem . Porosity and chemical resistance
are the issues , along with of course conductivity and catalytic properties .
Quote:

Another thing to try of course is TiO2 powder dispersed in the Co(NO3)2 solution...analogous to what Beer did.


Why TiO2 ? TiH2 powder instead maybe , but why should more of the same "interface" be desired when the interface material will be a lowered quality of the same material , only made thicker . Wouldn't it be better to invest experimentation in something different , instead of more of the same ?
Quote:

If neither of these things work then I'll probably give up on cobalt myself.


Then you might as well quit now because that TiO2 idea
is unlikely to go anywhere and when it fails as expected
it won't have done anything except confirm an expected
result for a way that Co spinel is unlikely to be useful .
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Rosco Bodine
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[*] posted on 12-12-2007 at 13:32


Quote:
Originally posted by dann2
Hello,
The patent have shown (pure) Co Oxide (making Chlorine anyways) to have worked for 250+ days continous with only a small rise in voltage. I call that success.

Yeah if chlorine is what you want to make , then a chlorine selective anode would be great for that . Hmmmm....
last time I checked it wasn't chlorine that were are wanting to make .
Quote:

They were not making Perchlorate though. Perhpas it is much 'easier ' on an anode making Chlorine in a controlled Chlorine cell as opposed to making Chlorate in a non controlled cell (High pH). None of the Co Oxide patents have used the Co Oxide to make Chlorate (in a controlled cell or other wise) that I am aware of.

Yeah I think an oxygen selective anode , and better yet a coating which is catalytic for perchlorate , would be the idea .
Quote:

Some of the patents have sang the praised of Zr in conjunction with Co in the spinel but the examples at the back of same did not show a Zr containing spinel doing anything out of the ordinary that I could see.

You are reading more into the patent than is there .
All it said was that among the several modifier oxides
that the Zr was "preferred" ..... preferred by who and for what use ? It didn't disclose that .
Quote:

The patents are obsessed with voltage accross cell = power used. This is not so important to us. We want a long lasting anode, a volt or so is not a problem.

Correct , but you have to interpret the data for what it says , not read into it what you want to find . The charted results
are showing potentials to show the efficiency of the interface materials as conductors , which allows for as little waste of
power as possible , so that more of the energy goes into conversion of the electrolyte , and isn't wasted power as heat warming the resistive coatings .
Quote:

Zr is the answer I tell you....

Dann2


Don't let Zr become your new Sb , as both will be a stone in your shoe .

Bismuth is a perchlorate specific catalyst in anode coatings . I did mention not to throw away the SnO2 just yet .

http://www.wipo.int/pctdb/en/wo.jsp?WO=1979%2F00842&IA=W...

[Edited on 12-12-2007 by Rosco Bodine]
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[*] posted on 12-12-2007 at 15:17


Quote:

Adhesion isn't the problem .


Adhesion seems to be an issue with the anodic electrodeposits I've tried (and I think Xenoid would agree with me). If the oxide can be easily wiped off with a rag, why bother even putting it in a cell? (IIRC, Beer mentions adhesion as being a problem wrt noble metal oxides on titanium metal).

Quote:

Porosity and chemical resistance are the issues , along with of course conductivity and catalytic properties .


Once you get past the threshold issue of having it adhere to the substrate in the first place, then, yes.

Quote:

Why TiO2 ? TiH2 powder instead maybe , but why should more of the same "interface" be desired when the interface material will be a lowered quality of the same material , only made thicker . Wouldn't it be better to invest experimentation in something different , instead of more of the same ?


AFAIK, none of us have yet done anything analogus to the examples given in Beer's patent #3632498. Since this patent apparently represents what may be the most industrially successful anode so far, it seems worth it to me to give it a try.

Quote:

Quote:

If neither of these things work then I'll probably give up on cobalt myself.


Then you might as well quit now because that TiO2 idea
is unlikely to go anywhere and when it fails as expected
it won't have done anything except confirm an expected
result for a way that Co spinel is unlikely to be useful .


Perhaps, but I really think it's a little too early to say that the TiO2 idea won't work.
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Rosco Bodine
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[*] posted on 12-12-2007 at 15:28


Look at the claims page on the patent above where
TiO2 was used as a modifier oxide in that coating scheme ,
and notice that Ruthenium goes right along with it .

Cobalt spinel is *not* an equivalent substitute for ruthenium . It works on titanium by way of an entirely
different method involving *interface* formation .
It does *not* form a solid solution with TiO2 as an isomorph RuO2 , but works by a different mechanism
involving spinel layers a few angstroms thick , not
diffusion layers that are microns thick .

I don't know and can't conceive how you think these mechanisms are interchangeable , no way , no how , not even maybe . That is why TiH2 powder was used along
with cobalt spinel , so that the spinel could fill the grain structure as a matrix of thin layer bonding the aggregate
of TiH2 or suboxide bimetal spinel reaction product .
It won't work with TiO2 , and if it did , then why even bother to etch and hydride the Ti substrate in the first place if you expect the TiO2 is such a swell mix with the
spinel ? What you are proposing doesn't make sense .

The first part of what you were saying about using Mn
as a component *does* make sense , because Mn along
with Fe , Ni , Bi , Pb and some other things can increase the oxygen overpotential , which is needed to be done for
a perchlorate anode .

[Edited on 12-12-2007 by Rosco Bodine]
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[*] posted on 12-12-2007 at 16:03


At this point, I'm more concerned with empirical results than I am with trying to identify a mechanism.

If you look at patent #3632498, you'll see that Beer mixes TiO2 up with everything but the kitchen sink (e.g., gold, iron, lead, ruthenium, etc). He claims:

"Iron oxide itself is highly sensitive to hydrochloric acid at room temperature, and so
are several titanium oxides. It has been found, however, that when a CO-precipitated mixture of iron oxide and titanium oxide is applied to a basis of conductive material it is only affected by hydrochloric acid at room temperature to a very smalI extent.

Similarly, ruthenium oxide coated on a titanium base, connected as an anode in an
alkali metal chloride electrolysis, which anode is contacted with the amalgam formed in a mercury cell, loses a part of its thickness after a prolonged period of electrolysis, because the reductive properties of the amalgam convert the ruthenium oxide into metallic ruthenium, and the metallic ruthenium is readily dissolved in the amalgam
from the surface of the titanium and is not resistant to the electrolyte. Co-precipitated mixed oxides of titanium oxide and ruthenium oxide, however, which are in contact with such an amalgam are resistant to the amalgam because these oxides when in mixed-crystal form are not reduced and so do not dissolve in the amalgam or in the
generated chlorine".

I don't know if it makes sense, all I know is that one of the most successful inventors claims that it works; so I'm just saying, I think it's worth a try.

[Edited on by jpsmith123]
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[*] posted on 12-12-2007 at 16:27


You aren't saying the same thing as the patent is describing when you talk about mixing already formed TiO2 as a filler with Co(NO3)2 . Beer is talking about *Coprecipitation* of isomorphous oxides which then
fuse to solid solutions , which is different .
What beer is talking about would involve using
a precursor for the TiO2 , not the already formed TiO2 itself .
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[*] posted on 12-12-2007 at 16:41


Well, yeah, but then he goes ahead and gives examples like XXI, where he uses the already formed oxides.
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[*] posted on 12-12-2007 at 16:53


Yeah and he used *Ruthenium* in ex. XXI when that approach is followed , which is exactly what I have been getting at .

Now on the other hand , cobalt aluminate is an example
of a spinel rather than an isomorphous oxides mixture ,
which can coprecipitate , but for this and for the
other MMO's as well , spinel or amorphous solid solutions , it is a pyrolytic process in most cases . You might find
a rare exception , good luck , because the minimum formation temperature is usually a few hundred degrees ,
but a few are lower .
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[*] posted on 12-12-2007 at 17:21


Just checked the chlorate cell, after exactly 6 days, the electrical parameters are unchanged. The current had dropped a little before, because I checked it early morning and it had probably cooled down a bit. The coating is starting to thin noticeably!

The perchlorate cell is crap, and will only last a few more hours!

Stop running around like headless chickens, and do some basic systematic studies.

BTW why not try Ruthenium Chloride and Butyl Titanium or whatever, and make a "real" MMO coating, are these chemicals completely unobtainable or prohibitively expensive, you only need a few mls. of soln. to coat an anode. But I believe they will still only be suitable for chlorate. I assume the industrial coatings are optimised for chlorate production, I guess there is no need to produce an anode coating that goes from chlorate to perchlorate in a single step. The chlor-alkali industry is absolutely huge, the perchlorate industry is miniscule in comparison (Rocket propellents, pyrotechnics - anything else?). The perchlorate industry just uses cheap chlorate and uses specialist coated anodes to make perchlorate. There is, from what I can gather, no need, or reason for industry to develop an anode coating that would be capable of going the "whole" way, which is really what amateurs desire. It is more efficient to use two separate processes, each of which is highly optimised........ not sure where I was going here, I've lost my thread....

Four coats of simple Co oxide has just about got halfway through a chlorate run, it should be able to tweak it a bit to go a full run and beyond. The perchlorate is a bigger problem!
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[*] posted on 12-12-2007 at 17:32


IIRC, there are other examples in his subsequent patents using preformed oxides...and some of these are not Ruthenium.

In any case, apparently every single example of Beer's involves baking at high temperature. Right now I'm trying to figure out the cheapest and quickest way to bake these things.
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