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Swede
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First LD Anode use
Rather than continue the Bucket Cell Adapter thread on this page, I hope you guys don't mind a separate thread because this is going in a new direction... the hardware
will be used to test the anode I created in January using the vibrational/rotational LD plating bath rig.
I plan on creating a small perchlorate tank using a transparent food container and the Bucket Cell Adapter (BCA) hardware. Normally I would advocate
that a transparent tank is not necessary for most home electrolysis efforts, and I stand behind that in general, but for the first runs with this
anode, I need to be able to see what is going on. I am going to make a special trip to a store that offers high-end food containers today, and set it
all up with the BCA hardware. For reference purposes, I also wanted to take a few microscopy photographs that show the velvety, crystalline surface
of anode #2, now called LDA2.
It's hard to take nice pictures. I have an excellent Meiji binocular microscope that is a joy to use, and every time I look through it, the image is
3D and quite breathtaking. I've tried eyepiece cameras, but the cheaper varietites do not work well, and the best pics come from a good digital
camera focused through the eyepiece; plus, a bit of editing, mostly cropping the black surrounding area.
The edges of the MMO anode gathered more LD than the remainder, creating warts and bulbs that are not pretty, but in reality, they will help
structurally. The fact that they grew together tells me that the possibility of electrolyte leaching under an LD edge is minimized.
Under the microscope:
And getting closer and closer:
The odd little fibers are actually cotton or paper towel fibers gathered by the anode. On a microscopic level, the anode is like velcro or sandpaper,
and in fact the surface feels exactly like 400 wet/dry silicon-carbide paper. Over the months, it has collected these little fibers that are
invisible to the naked eye, but show up under the microscope.
The color is not reproduced well. These pictures appear silvery, but that is due to the reflected powerful lighting used to create the photographs.
The actual color is an odd gray/black that changes color based upon the angle and amount of lighting. Under higher power, you can see the individual
LD crystals themselves on the surface of the anode. The anode weighs exactly 197.00 grams. After use, a further weighing should revel erosion, if
any.
The next step (today) is adaptation of the bucket cell hardware to a "Click-clack" food container of approximately 4 liters. More to come! 
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Eclectic
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Umm.....Is the container PET? Sure it will be inert to your solutions over time?
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patsroom
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Sorry Swede, I can not wait for the end results. Please Hurry! In the mean time are you going to be dosing HCI into the tank while running your test,
and are you going to start with fresh Chloride. Are there any other things that you might be doing as you are running the test set-up?
If I remember right you were not very happy with the clear containers you used before. But you did find that they helped you to see what was happening
in the cell and I would think that is the only reason you would use one now. The use would be for short term testing only.
Pat
[Edited on 3-12-2009 by patsroom]
[Edited on 3-12-2009 by patsroom]
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hissingnoise
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Some kind of large glass jar would seem to be ideal, since under the conditions of use the transparency of most plastics will reduce to the point of
translucence fairly quickly.
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watson.fawkes
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Quote: Originally posted by Swede  | | I plan on creating a small perchlorate tank using a transparent food container and the Bucket Cell Adapter (BCA) hardware. |
You might consider making a sight glass adapter to go with your electrode adapter. Use all the same construction techniques, except
instead of perforations just put a pane of glass. You know you want an excuse to try out the alternate construction technique anyway.
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Bikemaster
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Can't wait to see your anode in action!!!
Will you start from chloride of from chlorate?
Will you try your other LD anode ( the one with the bizare coating)?
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Swede
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I just realized the title of this thread is deceptive, as if it's already in use... sorry about that.
@ Pat: From the beginning, I decided I wanted to execute a two-step process - harvesting, washing, drying, and stockpiling chlorate for later
conversion to perchlorate. The Chloride to perchlorate process is possible, and LD should do it, but by going two-step, I can keep the product a bit
purer, and in the end, what falls out of solution should be pretty clean KClO4 due to its horrible solubility. Both chloride and chlorate should
remain behind. So this cell will start with raw (not recrystallized) potassium chlorate at an elevated temperature. I plan on preparing the solution
at about 50 degrees C to dissolve as much as possible, quickly assemble the system, and hit it with current to keep the temperature up and avoid
premature crystallization of chlorate by early cooling of the liquor.
The starting chloride will be residual and probably less than 1% of the solid, and perhaps less than 1/2% by weight in solution. If it turns out that
recrystallization of the chlorate is required prior to further electrolysis to perchlorate, then some rethinking (for me at least) may be in order.
LD is supposedly rugged and should handle a bit of chloride. We'll see.
The bucket cell hardware was engineered to take the LD anode, back when I was making electrodes with 3/4" wide straps rather than 1". It will not be
able to carry the same current as the larger strap, but should do the job.
@Hissingnoise: The clear container I've used in the past (successfully) with Pt anodes is some type of polycarbonate, and survived the process with
little fuss. Overall, perchlorate seems far more benign than Cl- --> ClO3. The theoretical yield per coulomb is higher, and the overall
transformation generally faster at a given current. If I can get 1 or 2 runs, that will be adequate. But I do want to see if the anode is shedding
or suffering physically.
Of the two LD anodes I made, LDA1 was a POS and mechanically is falling apart in its storage bag, with flakes of LD at the bottom. I doubt its
ability to do a decent job. Maybe later. LDA2 is the one pictured.
@ WF: I can't wait or delay any longer.  Future Bucket Cell Adapter #2 will
be a deluxe variant, but I need to give this one a shot. Earlier, a liquid level sight glass, made from an old pipette, clogged hopelessly in a
previous chlorate run. To correct this flawed methodology, the new system consists of a cut and flame polished medium-bore pipette section that slips
into a teflon fitting at the top of the cell. To measure the liquid level, a finger is placed over the pipette, and the pipette pulled from the
fitting, retaining the liquid. The natural volume marks on the pipette will let me know where the upper liquid level is, and this sort of system will
not clog compared to an external sight glass.
The use of Pt generally creates an interesting ozone smell, and I am curious to see if LD behaves similarly. dann2, did you ever notice an O3 odor
with lead dioxide?
I have 3 continuous work days starting today. I hope to have the cell running on Monday or Tuesday, 7 or 8 Dec.
Karma appreciated. If it works, I am going to set the LD plating rig back up and try making a few LD anodes, testing to see if a lighter plating will
do the job. Not a flash of LD, but not necessarily a 1/4" or 6mm thick plate either.
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Swede
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I forgot to mention, it will be interesting to see how the LD deposited over pure titanium will behave. In this picture, the flat section at the
lower left is the welded continuation of the anode strap, and is not MMO coated, but plain CP titanium. Before plating, it saw the same
degrease/surfactant soak that the rest of the anode did. I plan on submerging it fully, and if the plain LD over Ti survives and contributes to the
reaction, then the process to plate the anode may apply to CP Ti tube or similar, and may not be limited to MMO.
The MMO was brand new deNora MMO mesh, not the Laserred stuff.
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hissingnoise
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It's nice work Swede---you're all set for long perchlorate runs. . .
I'd think twice about submerging the anode-strap,though, just in case!
And if you want NH4ClO4 you can always switch to NaCl.
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watson.fawkes
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| Quote: Originally posted by Swede | | Future Bucket Cell Adapter #2 will be a deluxe variant, but I need to give this one a shot. Earlier, a liquid level sight glass, made from an old
pipette, clogged hopelessly in a previous chlorate run. |
I should have been clearer. I wasn't thinking about
a sight glass tube, but a sight glass window. It would use the same construction pattern as your existing adapter: two plates, gasket, screws. If
you're using it to monitor liquid level, a decent window dimension would be 1" x 6" or 1" x 8". If you make two, you can use one for illumination. The
only concern I'd have would be to ensure the mechanical stability of the bucket if the hole is too long. This could be addressed with pins and
perforations (inside the gasket line) and/or a tension strap around the bucket. The point is that you could use the same cheap (opaque) buckets as you
conceived your original adapter for.
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dann2
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Hello,
I have noticed Ozone from LD Perchlorate cells as they come to the end of the run. LD has been used for Ozone production.
About the bare Ti that has been plated. It will be difficult to know what exactly is going on with it (if using that part of the device as active
Anode area in solution) as it may well be supplied with current from the LD on the MMO mesh if indeed the bare Ti passivates under the LD. I am
presuming there is a bit of an overlap between LD deposited on the MMO and the LD deposited on the bare Ti to allow this. None of the pictures show an
angle where you can see it well enough. A picture from the bottom of the Anode would.
I have always noticed it is impossible to get LD to plate into inner corners (like the corner where the bare Ti edges meets the MMO mesh). It loves
to plate onto outside corners, hence all the nobbly bits, warts etc.
I do not think the LD will flake off the bare Ti but it is probably not as well bound to the Ti as to the mesh simply because of the physical nature
of the mesh/LD as opposed to flat-surface/LD (apart from the MMO coat which may help adhesion too).
Dunk the whole shaboo (MMO part, Ti/LD part and some of the Ti shaft) into the cell and see how it goes.
Regarding thickness of coating, LD Anodes do wear. The commerical Graphite substrate had 6mm (AFAICR) and lasted on average two years. With Ti the
same thickness will last far longer because if the Anode develops an LD fault the Anode substrate will not start to fall apart but will continue to
operate untill most of the LD is gone.
Thick coats good, thin coats bad.
Thick coats good, thin coats bad.
Thick coats good, thin coats bad. 
A transparent cell is good but you can never see as much as you hoped because of all the fine bubble in the cell. It's like trying to see through
dense mist. Putting a light behind the cell can help.
A demijohn (wine making yoke with two eye handle a the top) makes a great cell. Score a line around the jar close to the top and you can break off the
top using a hot wire. Use a sharpening stone to smooth off the sharp edge.
You get a nice glass funnell too, with handles on the bottom!
Consider weighing the Anode after is has operated for (say) one hour. It will be soaked with solution at that stage and will be a better starting
figure to go on. If you compare future weighings (a few days) to the dry weight you may find the Anode has increased! in weight (due to solution,
unless you wash and dry it).
Are you using one or two Cathodes?
It will be interesting to see if the K Perchlorate will stick to the LD Anode as it is formed. It did not with the Pt but it's much smoother.
Hopefully it will not or if it does it can be wiped off easily and not interfer with cell operation.
Good luck,
Dann2
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Swede
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Thanks for the encouragement, guys. I am off work today and am going to set up the bucket cell hardware with the LD anode. Unfortunately, it will
use only a single cathode. The volume of the container I chose is only about 4 liters, and should (if the system allows a decent amperage) be
concluded in no more than a few days. I think for the first run, I am going to immerse only the MMO portion. If that goes fine, then I will lower
the electrodes a bit and see what happens.
I'm guessing the thickness of LD on the bare Ti strap is maybe 3mm, no thicker. It forms what appears to be a solid mechanical continuation with the
remainder of the plating, and I can see the possibility of passivation of the strap portion, but if the coating is structurally sound, perhaps it will
remain intact, functional, and not fall off the Ti.
Since the anode rotated during plating, the coating is fairly even. The edge of the anode strap has a decent LD thickness on it. Perhaps the answer
is to keep the anode high enough so that the liquid level remains at least 10 mm below the upper edge. We'll see.
I do remember my Pt anode (a jewelry-trade plating anode) gathering some K-perchlorate crystals, but nothing gross, nothing that would truly interfere
with the process.
I'll snap a few pics of the rig as it is assembled today, 7 Dec, and tomorrow, it should be under power.
@W-F - I understand now, I thought you were referring to some sort of liquid level glass. I agree, there are cases where an attachable sight glass
would be a real advantage. I wonder if polycarbonate would do the job without fogging badly? Glass would work if drilled with diamond drills, but
the mechanical challenge with glass is high. Viton would be a good choice for gasketing.
[Edited on 7-12-2009 by Swede]
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Swede
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The small test cell is completed. I didn't realize initially how small my LD anode really is. It measures 8.9 X 4.6 cm, with a basic surface area of
0.41 dm^2. Given the convolutions, the surface as viewed under a microscope, and the mesh configuration, I am taking a wild guess and multiplying
this by 2.4 to determine the functional surface area. A major MMO manufacturer told me that their MMO mesh was 2.2 times the basic dimensions.
This yields a surface area of 98.4 cm^2 or 0.984 dm^2. I'm going to call it 1.0 dm^2 for purposes of current. Literature yields a range of 15 to 35
amps per dm^2, and my thoughts are 20 amps is a good starting point, which can be altered depending upon temperature, with 60 degrees being an upper
limit. The fairly small Ti strap is going to limit the current anyhow - this anode was made when my understanding of the limitations of titanium as a
conductor was not as good as it is now, and the strap is too small.
The cathode is titanium, and fairly small, yielding a higher current density at the cathode. For the first run, at least, I am not going to add NaF
or any other sort of additive. I want to see what sort of CE I can get in the native state.
The only other change I made was the use of viton gasket rather than skived PTFE gasket, with the hope that it will reduce the inevitable salt creep.
Tomorrow, I will mix up the chlorate and power it up.
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watson.fawkes
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| Quote: Originally posted by Swede | | I agree, there are cases where an attachable sight glass would be a real advantage. I wonder if polycarbonate would do the job without fogging badly?
Glass would work if drilled with diamond drills, but the mechanical challenge with glass is high. |
Polycarbonate is worth a try. I'm sure it's appropriate for some situations. If it does work, it means that solvent gluing is
appropriate for sealing.
As for sealing the window into the frame, my first choice would be to go with heat sealing. Put a rabbet/rebate (US/UK usage) on the inner surface of
the window, so that liquid pressure pushes the glass into the frame. Take a heat gun and heat up the rabbet until deformable, then press the glass in.
Then, step two, weld on a bead of plastic around the glass, sealing it in. This should seal initially, although I have to say I don't know how well it
will seal over the long term. Perhaps etching a border along the edge of the glass would help adhesion of the plastic onto the glass..
Alternately for sealing the window, treating as a piece of the bucket wall, meaning, it would have it's own bolt perimeter, gasket, and clamping ring.
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Swede
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After the preliminary microscopy photos, which will help me create some baseline images of the pristine anode surface, it was time (finally!) to
actually power the darned thing, and make some perchlorate with it.
For this test, I have gone back to a clear polycarbonate food container, brand name "Click-clack", for the first run, and it has a capacity of
approximately 4 liters. The transparency was desirable so I could see how the anode is doing physically.
The liquor was prepared by heating 4 liters of tap water to 50 degrees, and dissolving 600 grams of potassium chlorate, the raw product from previous
runs.
The small test cell was wired appropriately to my data-collection rig:
and my small notebook PC (using an 8 gig flash thumb drive) was fired up, using the DATAQ software for data collection of voltage, temperature, and
current.
Right away, I noticed that the bucket cell hardware was definitely not optimized for an LD anode. In my bucket cell adapter, I had spaced the
electrodes by 1 inch or 25 mm (don't ask me why I did this) and the voltage required to obtain a decent current (17 amps) was quite high at about 8.5
V. I also used a small cathode which made the problem worse. If I had two cathodes, and correct spacing, the voltage would be probably around 6.5V.
The temperature of the liquor at the start of the run was 50 degrees C, and is climbing slightly, a good sign, since it is easier to cool a cell than
to keep it warm. 20 amps was my target, but 20 amps was pushing the voltage limits on my power supply, so I decided to keep it at 17.
With the data collection at work, I should have a good feeling for the efficiency of the cell. So far, all appears normal. Plenty of hydrogen
evolution, and best of all, I am noticing a distinct odor of ozone, exactly the same as when Platinum is used.
I expect to see some solid perchlorate forming in a day or two. So far, everything looks excellent. More photos and text on my Lead Dioxide Anode blog for those interested. 
[Edited on 8-12-2009 by Swede]
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Swede
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3 or 4 hours in... the pH is climbing, and is at 9.5 right now. I've always assumed that pH in a perchlorate cell is not really a factor, but this
has me worried a bit. Otherwise, it's looking good, and the temperature has stabilized at 55 C.
Any thoughts on pH? I am hesitant to add HCl due to the chloride ions.
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dann2
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Hello,
All the commercial Perk cells that are discussed in Schumacher (book) as pointed out by Xenoid, are pH controlled. I don't know exactly why myself. I
seen studies were it clearly showed that CE is not related to pH. Can dig one out if you want.
Seen a study where they used Perchloric acid to controll pH. Not really an option.
Any Perchlorate cell I ran that I looked at pH it always went way up to 10 or so.
About the Cathode. You still can add two of them and put them close to the Anode. Simply bolt (or weld) some Ti to the existing Cathode (cut if off
short, about one half inch below lid) and route it around so that it forms a Cathode closer to Anode or indeed use two pieces for two Cathodes if you
wish. You won't have to mess with the lid. The bolts/weld will not cause problems as it's the Cathode.
Cannot say that I smelt Ozone at the start of any Sodium Perchlorate cell that I have ran. Could have missed it though. Definately get it at the end
of runs. Perhaps you get it more easily with a K cell?
Dann2
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Swede
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Report, day 2: Good news - Perchlorate is accumulating. Bad news - about 5 of the bulbous nodules on one side have fallen off the anode. Damn. I'm
wondering if I didn't sabotage myself with too high a voltage and not enough cathode area.
The edges of the underlying MMO anode were bare titanium due to saw-cutting of the original MMO material. If there is a consistent degradation of the
LD over bare Ti, but good adhesion on the MMO, then that would be a good clue.
I have dialed the amperage down to 10 amps to reduce the voltage.
I am disappointed, but the bulk of the anode is soldiering on, it is just about 5 separate warts that have parted company... but that is a bad sign
that the overall anode integrity is not as strong as I'd hoped.
Thoughts - A cylindrical form for the LD would probably produce fewer weak areas for this sort of failure. Surrounded by a larger tubular cathode,
you'd have a very even current distribution, and perhaps less erosion, but then you're back to the original problem of plating bare titanium, unless
you can obtain a cylindrical MMO anode to plate.
It's probably time to break out the plating rig again... argh, I hate plating LD, it gives me the creeps. But this time, I'll not stop with just one,
which was stupid. While the bath and rig are set up, it'd be best to plate several different forms if the bath can support it.
I don't want to overemphasize failure, it's just 4 or 5 edge warts, but I was hoping it would come through without any mechanical failure at all.
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Swede
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Another problem - the mesh holes in the LD are PACKED with crystalline perchlorate, and the surface of the anode is dusted with it. I attempted to
position the bubbler to kick these crystals off... we'll see. It may be physically difficult to make potassium (as opposed to Na) perchlorate
directly with LD.
Sodium would not have this particular issue. I don't know what effect it (the coating/dusting) might have, but it can't be good. If the coated areas
of the anode no longer conduct, then the efficiency will slowly drop to nil. On the other hand, what might be happening is that the perc forms on the
surface, builds to a certain mass, then drops off, exposing LD for additional conversion. The dusting of perc at the bottom of the tank would
indicate that there is a successful conversion.
We'll see.
Added: I'm already thinking about a new form of anode that should avoid edge erosion issues. Take a look at this picture from Titan:
Note that the periphery of the anode has a strip formed around it. Picture a primarily MMO substrate with strips of CP titanium welded onto it to
form a sort of frame. In a LD bath, if the anode is rotated, you are going to get some LD deposition on the framing strip, but it probably will not
adhere well at all, as the Ti oxides would form almost instantly. After removal from the LD plating bath, the frame is intentionally scraped clean of
all LD. What you end up with is a solid, well-secured, conductive LD mass within the frame, supported structurally by the MMO and the surrounding
frame, hopefully keeping edge erosion to a minimum.
[Edited on 9-12-2009 by Swede]
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Swede
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Some good news... Around 12:00 noon, I decided to replace the dinky cathode with something better, a box cathode:
Part of the problem was that I had selected a very small cathode, as supposedly, the current density on the cathode should be high for best
efficiency. But the voltage was too high.
The anode was also gathering significant amounts of crystalline perchlorate on the surface. Interestingly, the side of the anode AWAY from the
cathode was the one gathering crystals... the side facing the cathode was clean. I decided to replace the dinky cathode with the box, and while the
system was down, I could also take a look at the anode and try to find out what was going on with it, mechanically.
After this was made, the test cell was taken apart, temporarily. This is the anode inside the cell, away from the cathode. Note the loss of several
of the edge "warts" on the left side, and the accumulation of perchlorate crystals:
The anode was removed, washed in warm water, and then I gently manipulated the remaining warts to see if they were adhering well. The warts on the
bottom were quite strong. Those on the sides popped free easily. I decided to go ahead and remove all of the side warts, and it didn't take long.
The good news - wherever the LD had adhered to MMO, which included the faces of the anode, and the bottom edge, the adhesion was very strong. I tried
about 3X the manipulation on the bottom warts, which had an MMO edge (as opposed to a sawcut edge) and they didn't budge, so I left them there. The
system was reassembled with the box cathode:
With the power applied, I was very happy to see the voltage drop by about 1.5V for a given amperage. Right now, I am at 15 amps and 7.0V, and this
would be 5.5V to 6.0V if the spacing was better. The perchlorate is accumulating rapidly.
The anode in its current state wasn't what I started with, but at least I verified one thing - the lead dioxide plated over the MMO areas yielded a
strong adhesion which is very promising. If I had popped those warts free after the anode had been initially plated, it'd look as it does now. A bit
neutered, but what remains appears strong and functional.
So the news is, I'd say, about 75% good, and 25% bad. Properly prepared, it appears that LD does in fact plate over MMO very effectively. The real
test will come in a day or four. If there is no additional erosion at the edges, where the warts were popped free, then I'd say I have a smaller, but
strong and functional LD anode.
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dann2
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Hello,
O deary me. I am putting ashes on my noggen as I type.............
I would not be inclined to worry about a few warts falling off. In fact it will make the Anode less ugly , a form of beauty treatment for Anodes.
A piece of the MMO/Ti is now exposed to the solution, so it will be interesting to see if that part of the Anode falls apart. I don't believe it
will.
LD (as we have said before) simply loves to plate onto sharp corners and edges. This is why it was important to round off those
large Graphite substrate Anodes used in Nevada way back. The current density in the plating bath is higher at sharp corners
which gives a greater plating depth. I guess that when the warts get to a very large size (large radius of curvature) then the plating onto them will
start to approach a rate similar to flat area.
You could also put plastic pieces instead of CP Ti, and remove them when Anode has plated or perhaps put wax/hotmelt/tape etc onto the ends/edges to
stop the warts etc. Baffels were sometimes used in LD plating tanks to get less LD to plate onto areas of Anodes (like at edges). The baffle was
simple a piece of non conductor hung close to where less LD was wanted. It forces current to travel a longer path for to get to that place.
Going back to making Chlorate with Graphite. The erosion mechanism for the Graphite was thought to be both chemical and physical. (pH controlled,
commercial cells). The physical erosion came about by solid Chlorate forming inside small pours of the Graphite, expanding (crystals growing I
guess) and heaving out small lumps of Graphite. This is why it is important to seal up porous Graphite with Linseed oil (etc) so that this would not
happen much. Perhaps a similar thing will occur with the LD and K Perchlorate if solid K Perchlorate starts building up on/in the Anode. Never heard
of it mentioned with Sodium Perchlorate manufacture using LD. Hopefully this phenomen won't occur.
Just seen your last post. Consider putting plastic around the outside of the Cathode (where you do not want any Cathode really) to keep down surface
area. It is a very large Cathode (even larger of you add in outside surface). CD will be very low on outside. Then again Ti Cathodes are not supposed
to reduce Chlorate to Chloride much (I think). Not too sure about how good it is at reducing Perchlorate to Chlorate. Will look it up (if I can find
it). Perhaps it's my small Cathode fettish.............
Perhaps there was more gassing (higher CD) on the Anode side close to the Cathode giving more stirring and less K Perk. deposition??
Remember too that the warts that fell off easily would have gone onto Ti that was not even etched. It would have had Ti Oxide on it before you started
to plate. The acid bath would surly have manufactured more Ti Oxide as plating started. If using bare Ti you absolutely need to start with a
neutral/close to neutral Nitrate bath, or better still a Tartrate bath.
Just realized the bare Ti strap plated OK!!!!!!!! though.
Great pictures etc (as per usual).
How's the pH?
Dann2
[Edited on 9-12-2009 by dann2]
[Edited on 9-12-2009 by dann2]
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Swede
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It's been several days since I pulled the plug and allowed the small cell to cool. There is a respectable amount of perchlorate crystallized at the
bottom. Before the mod, (2X cathode + wart removal), the perchlorate was very white. After restarting with the hacked anode, there was a very light
dusting of black on the accumulated perc. layer.
Oh no...
But the good news is, this was very temporary, and the system continued to make white perc. I think what happened was that I had edge erosion for a
period of time after popping the warts free, but this concluded quickly. I was a bit afraid to look at the anode, but it looks exactly the same as
picture #5 in my post above. No obvious, visual additional erosion. That may be a good sign.
This perc batch, since it has LD in it, will be hot-filtered and recrystallized. The anode will be weighed, and another run made, perhaps with a
superior cathode set. This second run will be much more pertinent in terms of further erosion, measured by weight.
The warts that popped free have a cool pattern to them on the interior, like tree growth rings, and it may show (under microscopy) the grain size and
forms of LD plated, since it should gradually progress from beta to alpha LD.
dann2, I have noticed very little variation in CE with Ti cathode size, at least with chlorate and MMO. It doesn't seem to care if if the cathode
current density is very low, or very high. I don't know if this also holds true with perchlorate and LD. I do feel like I sabotaged myself with a
poor setup, requiring excess voltage to get a decent current. I suppose I could have run at 2 amps for a month, but I'd rather not even bother with
that methodology. I want the published 20 to 35 amps/dm^2 per the literature, and a run that is measured in days rather than weeks. No one wants to
baby-sit a cell for 6 weeks.
The pH peaked at 10.5 and normally hovered around 10.0. As usual, the perchlorate cell was cleaner, less fussy, less salty, and better-behaved than a
chlorate cell.
Future LD plating attempts will focus on surfaces without sharp angles, if possible. Failing that, then I am going to try a "framed" MMO mesh. I
genuinely feel that the adhesion of LD to MMO is excellent if the surface is properly prepped. This is indicated by edge erosion. If the weak point
is at the MMO/LD interface, then the edge erosion will show an undercut. If the erosion is primarily due to coarse or weak LD crystal formation, then
the erosion should show a rounding effect where I popped the warts free. And what erosion I initially see is more rounded than undercut. Where LD is
plated on MMO, adhesion seems excellent, borderline outstanding. If this is the case, then LD plating technique is the culprit, rather than substrate
failure.
When I free the anode, I will take more microscopy pics that should reveal the truth of this hypothesis. Best case is that no further erosion will
occur, and I may yet have an anode that will do good duty for perhaps months.
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dann2
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Hello,
| Quote: Originally posted by Swede | dann2, I have noticed very little variation in CE with Ti cathode size, at least with chlorate and MMO. It doesn't seem to care if if the cathode
current density is very low, or very high. I don't know if this also holds true with perchlorate and LD.
The pH peaked at 10.5 and normally hovered around 10.0. As usual, the perchlorate cell was cleaner, less fussy, less salty, and better-behaved than a
chlorate cell.
Future LD plating attempts will focus on surfaces without sharp angles, if possible. Failing that, then I am going to try a "framed" MMO mesh.
..............
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The framed MMO will help to carry current to the Anode if you weld (which you are probably going to do anyways) the frame to the MMO here and there.
Perchlorate cells seem to be less 'corrosive' than Chlorate cells. Pity they eat most Chlorate Anode materials though! Perchlorate cells have a much
shorter run time too which gives less time for creeping salt problems too.
Look carefully at the Cathode and see can you see any Lead metal appearing on it. It would be very hard to see any (if it's there at all) as it is a
large Cathode and the run time you have given the Anode is fairly short.
Perhaps the Cathode area is not that important. I have no idea how much CE improvement you will get per square cm you decrease etc. Some materials are
better at reducing the wanted products back to the starting materials. Titanium is good in this respect, compared to steel/Iron/SS.
12AX7 ran a large Graphite Anode Chlorate cell with a hugh Steel Cathode, controlled the pH somewhat (added acid each day once) and got very low CE
(less that 20%?). He blamed the hugh Cathode.
In a Perchlorate cell (AFAIK) we have reduction of Perchlorate going back to Chlorate (damm all I think) and reduction of Chlorate back to
Hypochlorite. Ti will not reduce Chlorate, Iron will (I read somewhere). Don't know about reduction of Perchlorate at the Ti Cathode. So size of a Ti
Cathode may not be an issue at all but the size of an Iron Cathode may be very relevant (at least without additives (Chromate) to stop reduction).
Then again with a LD Anode when you get some erosion you will get Lead metal on the Ti Cathode and end up with a fluffy Lead metal deposit. Hugh
surface area of Lead. I have no idea how Lead operates as a reducer of Chlorate or Perchlorate when used as a Cathode, so size of Ti (it will be Lead
really as cell progresses) may be important (when using LD, because of erosion of LD).
In your case Voltage is a bit scarse so you have to go for large(ish) Cathode.
As I said before perhaps I have a small Cathode fetish........
Just wondering does the Chloride content of the cell increase as you run the cell? Perhaps you could test for it some time.
Cheers,
Dann2
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12AX7
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I do indeed believe my large (and ferrous) cathode was the cause of poor chlorate efficiency. Perchlorate efficiency was excellent though; I probably
over-ran the anodes a few times, expecting lower efficiency than I actually got.
Tim
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Swede
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I've been at "real" work for a couple of days. This afternoon, I will take the system down further, free the anode, and look closely for lead on the
cathode, and what type of erosion (if any) I see on the edge of the anode.
I hate to keep beating this drum, but everything I've seen says that without exotic surface prep, bare Ti will not take a good LD plate, but the MMO
does. When the factories make MMO mesh, they apply their "trade secret" Ti surface prep prior to dipping and baking the powdered MMO slurry, or
however they do it. I say we take advantage of their hard work, and with the availability of surplus MMO at inexpensive prices, use that as the
substrate for plating.
If examination (and further runs) show no additional LD erosion at the edges, then a frame may not be needed. Simply execute a decent plate job on a
cut and prepped MMO mesh, and if you feel the need (I do now!) pop the edge warts free and grind them up and save as a reasonably clean source of LD
on a small scale for other applications. What remains is a well plated and attractive LD anode.
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