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dann2
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The END has arrived
Hello,
Thought I would stick this in this thread since it's LD.
My Ti substrate LD Anode was shelved for approx. 6 months and then placed into a Perchlorate cell from a previous Graphite Anode cell (liquor which
was taken to 30 grams per liter Sodium Chloride from a saturated solution of Chloride). It ran for approx. 3 weeks at 1.75 Amps until the last of the
Lead Dioxide fell off. The Lead Dioxide fell of in two slabs of approx. 1.4cm squared each. There were no drilled holes in the Ti substrate at the top
of the Anode where this LD was. The thickness of the LD that fell off was measured to be approx. 1.3mm. This compares to a starting thickness of
approx. 1.5mm in that top area when the Anode was new. There was no visible erosion of the Ti substrate. The cell contained no Fluoride which was
blamed for Ti erosion in the previous cell run. There are still parts of the Anode with LD still clinging to it around the holes etc. There are also
areas of the Ti which still have Tin Oxide on them as they are gassing when current is passed. The Anode still draws 1.75 Amps funny enough. Tin
Oxide is tough stuff. No tests for CE were made. Some brown deposit of LD can be seen on the cell bottom.
The Anode has clocked up a total of 4.7 months in various cells.
It's time to make a new one!
Previous adventures and all guresome details with this Anode can be seen here
Dann2
[Edited on 12-1-2010 by dann2]
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Swede
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Dann2, what effect (if any) do you think fluoride has on lead dioxide anodes, or by extension, on the cell chemistry itself? The whole area of cell
additives seems to start and end at dichromate and fluoride, and this is one of those areas where, unless the cell chemistry is well known, it is hard
to determine what effects these additives have. If there is a helpful additive that can be removed during purification, and isn't overly toxic, it'd
be very helpful.
I need to get off my rear and try welding up some suitable frame-like substrates for further LD tests.
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Rosco Bodine
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Quote: Originally posted by Swede  |
I need to get off my rear and try welding up some suitable frame-like substrates for further LD tests.
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Bismuth may be a thing to keep in mind there .......oh the beauty of hopper crystals , maybe it's a clue to see a rainbow there with sacred geometry
All Aboard
http://www.youtube.com/watch?v=dBawQqcNfog&fmt=18 Still Searching
[Edited on 17-1-2010 by Rosco Bodine]
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dann2
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Hello,
If using Titanium substrate anything, Flourine is out IMO.
There is a paper (Perchlorate making) here giving info. on using Persulphate as an additive. It also uses Sulphuric acid (and both F and Sulphate) to both lower pH and as an
'additive'. The paper says that pH effects CE and also how effective each additive is. I have read papers that say the opposite, ie. pH has no effect
on CE. It's all rather complicated and it depends on Anode age, CD, temperature etc etc etc. I am not up to speed on the best conditions to use for
(say) a bucket cell, or indeed any other design. They also say that high pH gives LD erosioin (bad, very bad IMO).
Chromates form a film on the Cathode that keeps Chlorate, Hypochlorite, Perchlorate etc away from the Cathode but allows water and hydrogen through.
It also acts as a pH buffer and lowers Oxygen generation at the Anode. According to a thesis my Linda Nylen (spelling) that was uploaded here
somewhere, Yttrium compounds will do the same job and are not toxic.
Chromates are out for use with LD (don't know about Y) as they form a film on the LD which lowers CE.
F does the same as Chromates, don't know if it forms a film on the Cathode or what.
Don't know how Persulphates work.
Link here to a patent that uses Persulphate as an additive for Perk making. It uses LD. The use of Persulphate seems to be associated with LD and Perk
making.
I don't really know if Persulphate is a useful additive for Chlorate making or with what Anodes.
My own attitude to additives is to leave them out. Stay green. F is definately out for Ti substrate anything. Chromates are toxic. Yttrium not easy to
get. Persulphate only helpful (I think) with LD during Perk. making?
Use high current density on Cathodes to help keep reduction of species as low as possible. Remember the CE advantages are not huge in regard to
additives. It would be a joke to add additive to a Chlorate cell that is hot pH controlled.
Then again if using an expensive Pt Anode in very clean Chlorate (no Chloride) to make Perk. it seems sensible to add Chromate to help keep Chloride
from appearing (reduction of Chlorate) and protect Pt Anode from erosion.
All clear as mud!
Genuine batch processes (like we do) where Chloride (or Chlorate) is added to a cell and that cell is then run to low Chloride (or Chlorate)
concentration will ALWAYS give lower, less impressive CE's than quoted for industry no matter what additives or what not we employ.
Swede, why don't you get yourself one of those office chairs with wheels. You can keep your rear end where it is and propell yourself about the garage
from bench to bench.......
Dann2
Dann2
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dann2
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Hello,
One more on LD plating onto Graphite using ceramic particles in the LD plating tank. Tested in Perk. cell too.
Thanks to www.Solo.library.com !
Cheers,
Dann2
Attachment: ld_beads.pdf (526kB)
This file has been downloaded 1463 times
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Swede
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Sulfuric acid seems like it would be an ideal pH controller for a perchlorate cell sensitive to chloride ions. All that would be left behind in the
end would be soluble sulfates, which can be removed in the washing/recrystallization process. If a high pH (inevitable with an uncontrolled
perchlorate cell) is truly hard on LD (and it wouldn't surprise me) then sulfuric would be a decent option.
I am more interested in additives in a perchlorate cell more as a means of reducing or eliminating erosion that in increasing CE. Chromate are out, I
won't use them for this process. If there are easily-removed additives that protect Pt, LD, or both, then it might be worth pursuing.
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quicksilver
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Would it be possible to accomplish two objectives at once with a bar of lead oxidizing WHILE IT IS BEING USED THUS MAINTAINING THE PbO?
It just seems that is not so impossible an objective.
The other thing that struck me (no pun) is that the technique for making Teflon coated bullets could be used with gouging rods with PbO. You would
need an oven that someone would not want to cook in ANYMORE however. Powdered Teflon, graphite, PbO and a rod....
[Edited on 6-2-2010 by quicksilver]
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Xenoid
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| Quote: Originally posted by quicksilver | Would it be possible to accomplish two objectives at once with a bar of lead oxidizing WHILE IT IS BEING USED THUS MAINTAINING THE PbO?
It just seems that is not so impossible an objective. |
Well, it may just seem that way to you. 
Do you seriously think industry spent many millions of dollars and over half a century searching for MMO when they could have just used lead anodes.
Why would they use expensive platinum in perchlorate cells when they could just use good old lead!
Why don't you try putting a lead anode (even one with a lead dioxide coating on it from electrolysis of dilute sulphuric acid) in a chlorate or
perchlorate cell. You'll get an instant messy mix of white, yellow and orange chloride and oxides!.
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quicksilver
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I know next to nothing about this industry specifically, so I can't really maintain a reason for the lack of use of PbO (I simply don't know enough
about it) however it has worked for some electro-chemical concepts in the past. My guess is that lead per se' is just a no-no and working with it
carry's too many hassles. But for a hobbyist agenda these MAY be overcome.
Actually I was genuinely asking a question because PbO pops it's heavy little head up periodically in these discussions.
Industry has different needs, etc. I was reaching because we appear to be channeled to a choice between MMO or carbon - -yet...PbO continues to come
up in discussion regarding cell design. So; it's really a dead-end?
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Xenoid
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No - of course not! Lead dioxide is one of the best anode materials available, able to make chlorate and perchlorate efficiently. Unfortunately, like
many coating materials it tends to be porous and will allow underlying anode materials to be eroded unless they are "valve" type metals (titanium,
niobium, etc.). Such metals rapidly "passivate" at the point of attack, by becoming coated in a protective, impervious, oxide layer, thus preventing
further erosion.
Lead dioxide is a good electrical conductor so if you can make a "solid" LDO anode or coat an inert material (even plastic) readily available to the
amateur you will have made an outstanding contribution - good luck!
All your questions have been answered many times over, in the multitudinous chlorate/perchlorate and anode threads on this forum. Have you not read
any of them? There are also several fine websites, and many publications online, please avail yourself of them.
[Edited on 7-2-2010 by Xenoid]
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12AX7
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As far as using Pb or PbO directly as an anode, the latter is not very conductive, while the former does oxidize to PbO2 on the surface, but the
interface layer consists of PbO and PbCl2 which are poor conductors. The result is a slowly flaking electrode and very little electrolysis of the
solution.
Tim
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mnick12
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I know little to nothing about electro-chemistry, but I think some of you who have been interested in making our using lead dioxide anodes may find
this page interesting http://resources.metapress.com/pdf-preview.axd?code=h5726026... .
It outlines the preparation of both alpha and beta PbO2.
A quick question, it seems as though beta PbO2 is preferred over alpha PbO2, why is that? Is one more durable than the other?
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Contrabasso
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Years ago I worked in a big plating shop. The "Chrome" was put on in a huge automated machine. The plating order was (on top of steel!) flash nickel
for adhesion, levelling copper for its ability to level the surface (saving hand buffing) then three nickels there were three
slightly different nickel baths and they plated different grain sizes so that there was almost no porosity in the nickel then the top
coat was bright chrome.
Now I haven't access to the plant (it's gone and rebuilt as houses!) but if anyone can relate the grain size variants to the properties of led dioxide
plating system, could one plate three adhering but different layers to protect the substrate more???
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quicksilver
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Would not grain size variety need a micron measurement slide for a decent microscope? Else you'd be dependent upon things like "mesh" measurement
which can be all over the place.
I am really struggling with switching power supplies. The more advanced, the more difficult to understand them with no background paperwork. One of
the MOST frustrating things is that I have found problems I could have eliminated had I be much more professional in my wiring and simple matters. The
excitement to get something up and running is slowing me and it's a real bastard.
One thing that I have come to understand is that Lamda (the company not the man) had bought out MANY struggling companies in Calif. and there are LOTS
of good stuff out there (especially from the late 1980's) with NO paperwork. A lot of the rack mounted PSU and the heavy duty units designed for
automated plating shops have differing sensor mechanisms.
IF you found a Lamda rack mount that reads in the tenth of a volt with no load and applying a load of 10w brings it up, you can then hook up the unit
to your cell and the current will jump when the load is retrieved from the 5v output. HOWEVER there are some that lock at that current (Ratheon's
Sorensen 5-30). To unlock the current sensing (you need a DIMM in line at the 10A plug) have some higher load like an auto interior light bulb &
put that in place of the DIMM (or you'll screw your DIMM as it will jump to it top and drop down to what resistance it sees (there is a formula for
this which I don't know)
I also discovered something about the use of computer PSU's for this application. SOME units will cheat you out of current if you bunch the + leads
together. This does not occur on ALL computer PS what so ever. But some should be checked. I found one 400w that had this issue with the ground
(bunching them to form a single negative lead). I have found out a hell of a lot of things by learning from Woelen's original design; which I have
come to appreciate more and more. In fact, had I not found a electronics surplus and scrap yard I would defiantly get one of those 1000w supplies
knowing what I do now. Those things can be made to continually pump 30A with NO problem!
[Edited on 4-3-2010 by quicksilver]
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dann2
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Hello,
The full article is attached if anyone is interested. It's a djuv file and you will have to download a reader for to see it.
Regarding the Alpha/Beta my understanding is:
The Beta is stated to be the best wearing coat. It has higher conductivity too but I do not think that is really an issue as both have very good
conductivity. The Beta may have higher catalytic activity (better Current efficincy and will make the products at a slightly lower Voltage that Alpha,
thought that's a guess). The Beta is always used by industry.
I have seen Alpha on a Ti substate Anode exposed when the Beta fell off and it still worked away OK and lasted quite a long time. It was only a very
thin coating put on first as it is supposed to adhere better that the Beta.
Dann2
Attachment: AlphaLD.djvu (230kB)
This file has been downloaded 780 times
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Rosco Bodine
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alternating layers alpha PbO2 and beta PbO2
It would seem possible that a stress relieved PbO2 anode can be formed simply by varying the temperature of an electrolyte which produces the alpha or
beta modification
as a function of temperature. It would also seem possible that at an intermediate temperature a mixed deposit of the alpha and beta may
simultaneously be produced. Although these processes were not described, that is a reasonable conclusion which may be drawn from the attached
article.
A request is pending for the related later article from this past December which describes the beta PbO2 process.
A couple of ideas have occurred to me during the break for awhile in the discussion of plating schemes for PbO2. In the processes using lead nitrate
electrolyte, there is a use of copper nitrate and nickel nitrate and sodium fluoride as minor ingredient additives. I have some reservations about
these particular additives. It occurred to me that it may be useful more than nickel nitrate to use cobalt nitrate instead,
as a likely substitute, or perhaps manganese nitrate. Also
it would seem that any use of fluoride should be the ammonium salt and no fluoride whatsoever should be used in combination with any bismuth compounds
in the electrolyte due to the likelihood of precipitation of the virtually insoluble bismuth fluoride. It seems that bismuth
oxide could be applied as a pore filler sort of trace catalyst
on a PbO2 anode coating as a finishing step, and part or all of the bismuth oxide transformed into the fluoride chemically simply by a final dip in a
fluoride solution. There possibly could be a catalytic bielectrode effect produced by the couple between the PbO2 matrix and the Bismuth Oxide /
Bismuth Oxyfluoride / Bismuth Fluoride deposits in the pores.
Attachment: The electrodeposition of highly reflective lead dioxide coatings.pdf (423kB)
This file has been downloaded 2009 times
Here is the second article which describes the beta PbO2 electrodeposition at 60C.
Interestingly enough Bismuth is also capable of forming a concentrated solution or sol in a methanesulfonic acid aqueous system. See US6103088
attached. There are obvious implications here in these references for the usefulness of methanesulfonic acid in processes for production of anodes,
electrolytical processes obviously.
But it would seem also that a methanesulfonate of bismuth
and perhaps other materials of interest as dopants may have interest with regards to baked coatings.
[Edited on 14-5-2010 by Rosco Bodine]
Attachment: The deposition of nanostructured b-PbO2 coatings from aqueous.pdf (642kB)
This file has been downloaded 2413 times
Attachment: US6103088 Bismuth Methanesulfonate.pdf (45kB)
This file has been downloaded 964 times
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quicksilver
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I've followed the above w/ great interest. Commercial availability of Bismuth trioxcide (tech-grade) through pyro supplier chemical outlets is fairly
cheap as are nickel & copper nitrate. But most all fluoride/fluorine materials seem to be sold as reagent-grade only w/ commensurate price.
I would imagine that at the point of conductivity with minimal resistance, the percentage of binder would be low enough to allow use of "coating
material" (with low % binder such as SL or thinned potting epoxy). "Baked" coatings also appear attractive as to be a less time & $ intensive
route.
It just seems a damn shame to spend so much time on effective coating and see it all fall away after a few runs w/ high current. What's more at the
level needed for proper solutions the price tag's not low either. To loose the coating after, say, half a dozen runs is tough. For that matter, what's
the longest anyone has had a (DIY) coated anode stay coated for?
I have (somewhere) the conductivity tables of a great deal of materials & have learned via bridge-wireless ignition experimentation how to alter
this with highly conductive dopants. It appears within grasp to make a polymer electrode as conductive as needed w/ addition of some % or carbons.
{At this point, Ive gotten some damn nice PSU's and see no need to do runs in small scale BUT have seen the results of higher current on electrodes
& at or about >30A they take a real beating if the solution volume is under a certain level. We have seen the electrodes "curl away" from one
another on many occasions and this, I believe is one factor to the flaking off of surface coatings. The flat design of an electrode is a double-edged
sword.} This curling or warping effect is often due to the distance between electrode being closer than formula - however when distance is met surface
area may go beyond what is practical unless simple means are found to mfg.
The use of a cylinder (such as a graphite rod) virtually eliminates the curling effect when proximity of electrodes are closer. Instead of using the
flat perforated electrode, several cylinders [of each electrode] would possibly sustain a much longer life.
When it gets down to the nitty-gritty, it seems the coating of several graphite rods or bars may meet expectation of long life and highly efficient
operation.
In regards to baked coatings; I have shopped element metals for years now & found that price breaks occur in powdered form (even from high-priced
outlets like Alpha Asear). When dealing with oxides, technical grade (99.5% or poorer) are available in only certain products. Using reagent-grade
would bring price levels to a very poor return on the investment IF the electrode's life is low.
[Edited on 15-5-2010 by quicksilver]
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Rosco Bodine
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I'll have to look back through the earlier references, but it seems familiar and possibly the use of the same surfactant also benefits beta PbO2
electrodeposition
from a lead nitrate based electrolyte. There may be other electrolyte systems which would also produce a dense and stress relieved mixed allotrope
deposit
having high density. While doing some searching for these articles I also read that conducting the electrodeposition of PbO2 in an electrolyte which
also contains a sol of a different oxide, such as alumina and possibly other materials
results in an incorporation of the oxide of that sol in mixture with the PbO2, as a kind of matrix. This could produce interesting mixed deposits
having desirable properties.
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Zaratukhshthra
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Ag or Ag-Pb alloy substrate PbO2 anodes
US4345987 describes a Pb/Ag alloy substrate PbO2 anode. They claim the use of Pb alloy instead of pure silver increases the resistance against
corrosion of the electrode. But their comparative studies (corrosion tests) were done in aq sulfuric acid medium instead of chloride ions (the
electrode was not supposed to be used for ClO3/ClO4 preparation).
In the introduction part, there's a brief exlanation of silver substrate PbO2 anodes | Quote: | | Japanese Patent Publication No. 23947/16 discloses an electrode obtained by electrodepositing PbO2 on the surface of <b>silver
substrate</b> or a metal substrate plated with silver. This electrode has a very small contact resistance between the metal substrate and the
PbO2 coating. further, the electrode exhibits a sufficient resisiance against corrosion when it is used for the electrolytes containing
<b>halogen</b>, sulfides, chromates and carbonates that form sparingly soluble. silver. compounds, or for the, alkaline electrolytes.
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(any Japanese member?)
It's well known that silver is one of the best choices for connecting to PbO2 anodes. this is not because of low resistance of silver oxide
intermediate layer (simply because it's insulating) but the formation of a silver plumbate layer.
e.g. in US3017448 (electric battery) lead compounds are added to the active material of a silver electrode: | Quote: | In the presence of alkaline electrolyte, the
silver oxides and the lead or lead compound react to form
a coating on the silver oxide particles which has been
identified as silver plumbate, Ag2PbO3 or Ag5Pb2O6. This
coating or film reduces the gassing rate of a divalent
silver oxide electrode by a factor of about four, substantially
decreases the electrical resistance of such an electrode
and provides an electrode discharge which
[achieves] utilizes almost 100% of the theoretical divalent
silver oxide capacity at the upper voltage plateau. |
(P.S. this is my first post. Hello to everyone!)
Attachment: US4345987A PbAgSLD Anode.pdf (320kB)
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dann2
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Hello,
(correct thread this time!)
A good way do find out how the Pb/Ag substrate (when used in a LD Anode) would hold up in a Perchlorate cell (or Chlorate Ccell) would be to make a
small amount of the alloy and cast an 'Anode'. Use this 'Anode' in a Perchlorate cell and see how long it lasts. If it lasts quite a long time, (like
MMO or Tin Oxide on Ti) then it should be OK for a substrate in a Lead Dioxide Anode.
If it erodes like Graphite then it will not make a good substrate and will be comparable to Graphite as a substrate (a shit substrate for the average
garage operator). It will need a perfect coating (stress free, no pin holes, thick, etc) of Lead Dioxide which is not very easy to obtain in the
Amateur world.
A substrate that is tolerent of faults in the LD coating is extremly desirable.
Dann2
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dann2
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Nitrites in LD plating tank
Bump.
Document attached on producing Lead Dioxide from Lead Nitrate and Lead Perchlorate baths. Not much in it but it talks a bit about the problem of
Nitrites building up in the tank and causing a drop in plating efficiency.
They say this can be counteracted by adding Hydrogen Peroxide or using Pb304.
There is a graph showing plating efficiency versus 100*Nitrite/Nitrate ratio.
What does this ratio actually mean. If I have 300grams per litre Lead Nitrate and 10 grams per litre Lead Nitrite am I at the 100 X 10 / 300 = 3.3
point on the horizontal?
Thus 10 grams per litre Nitrite gives you about 42% plating CE if you have 300grams per liter Lead Nitrate.
US 2994649 gives a figure of an increase 0.1% Nitrite reducing plating CE down to 30%.
It's impossible (for me anyways) to interpret what the patent is trying to say (or hide).
The Patent mentions Sodium Nitrite (as opposed to Lead Nitrite) but thats just an error IMO or are they bizzarly giving the Nitrite content of the
bath in terms of 'Sodium Nitrite'
Anyhow, it's time I STFU and got out the plating tank.......
TIA,
Dann2
Attachment: PB02_NITRITES.pdf (158kB)
This file has been downloaded 1206 times
[Edited on 5-8-2011 by dann2]
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watson.fawkes
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| Quote: Originally posted by dann2 | There is a graph showing plating efficiency versus 100*Nitrite/Nitrate ratio.
What does this ratio actually mean. If I have 300grams per litre Lead Nitrate and 10 grams per litre Lead Nitrite am I at the 100 X 10 / 300 = 3.3
point on the horizontal? |
That's how I read it. The square brackets in the axis label denote activity, which
here is tantamount to concentration. The 1.6 mol / L concentration they're using is more-or-less a saturated solution of Pb(NO3)2.
What's interesting, though, is that they mention that the plating efficiency is up at 100% when the cathodic current density is low, ~ 1 mA / cm^2.
This seems like the easiest way to deal with the problem in practice, although it does necessarily increase the tank size. Optimum anodic density is
listed at 36 mA / cm^2, so maintaining a 36:1 ratio between cathode and anode areas is the minimum.
The authors also mention using buffers to get rid of "residual stress in deposits". I presume they mean mechanical stress on the resulting anode. As
this materially affects lifespan, this seems worth tracking down. They reference a paper by the same authors as "in press".
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dann2
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Thanks for reply.
That artical cost me twenty bucks!!
Its from the Institute of metal finishing. I thought it would be a bit longer and perhaps elaborate on the Nitrite thing a bit more. It's a subject
very little discussed in the patents and journals and yet seems to be very important. CE going to very low % is imporatant IMO.
Even in the elaborate patents by Gibbs (plating graphite with LD for commercial use back in the sixties) it is not mentioned. They have anti stress
and anti bubble stuff in the tank, namely ctab (cetyl trimethylammoniumbromate, spelling more than likely wrong). They wash the tank contents
(literally) using Amyl Alcohol to sweep out byproducts from the breakdown of the ctab as it effects plating badly after some time.
Perhaps the Amyl Alcohol washes out nitrites too? I would be inclined to think not as Nitrites are very similar to Nitrates (it doesent make sence for
an alcohol to 'dissolve' nitrite ions to me anyways.).
Perhaps its a detail left out to confuse a patent thief.
Remember that the paper posted above is not in direct relation to Anodes for Chlorate and or Perchlorate but battery stuff.
Dann2
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watson.fawkes
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| Quote: Originally posted by dann2 | | I thought it would be a bit longer and perhaps elaborate on the Nitrite thing a bit more. It's a subject very little discussed in the patents and
journals and yet seems to be very important. CE going to very low % is imporatant IMO. |
The point they made
about nitrites is that it's an alternate current carrier: "the nitrate ion is reversibly reduced to nitrite at the cathode and oxidized to nitrate at
the anode". So it's not presence of nitrite as such that causes the problem. Rather, the formation of nitrite is indicative of cell conditions that
promote this alternate current path. The amount of nitrite in the bath at any given time is correlated to the current partition between electrons that
travel through the nitrite path and ones that travel through other paths.
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dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
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Presence of Nitrites may (along with robbing current) give bad coatings of LD (for some unknown reason).
I of course have no idea if Nitrites do indeed cause a decrease in plating quality.
Reading (yet another) paper on Lead Dioxide. (ref section, a 2011 review of LD Anodes)
it states (and I quote):
............and for pure b-PbO2 typical conditions include:
(a) 1 M lead nitrate + 0.1 M copper nitrate (to avoid
Pb deposition and nitrate reduction on the cathode) in 1 M
nitric acid, 333 K, j = 50 mA cm2 then 20 mA cm2;..........
Will the presence of Copper Nitrate in a Lead Dioxide plating bath (using Lead Nitrate) eliminate or decrease greatly the formation of Nitrites at the
Cathode do you think?
I have never seem it mentioned or hinted at before, the Cu Nitrate being there to only stop Lead metal being deposited (wasted) on the Cathode.
Perhaps the Nitrites are only a major problem when plating LD from Nitrate baths when Cu Nitrate is not present (like battery applications, or simply
making LD as a reagent etc etc).
Funny enough the only (only two that I have ever seen) articles where it mentions Nitrite problems are in a reagent making patent (depositing LD for
making reagent) and the paper above (depositing LD for battery stuff).
Thanks for your time.
Dann2
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