Sciencemadness Discussion Board - Thoughts On Anodes

Thoughts On Anodes

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jpsmith123 - 30-12-2005 at 00:59

For quite a few months, I've been researching the question of anodes for small scale but serious production of chlorates and perchlorates.

In case anyone is interested, here are some of my conclusions so far:

(The following materials, as anodes, will make either chlorate or perchlorate).

Platinum

Extremely expensive, though highly efficient, and requires some process control for maximum longevity.

IMHO, the combination of high cost with non-negligible rate of erosion rules out platinum as an option for *serious*
production at home; at least as far as "batch" processes (i.e., processes where the proportions of ionic species change dramatically) are concerned.

If you want to make a few lbs. of ClO4 just to say you did it, Pt is probably the easiest way to go, IMO.

***************************************

Lead Dioxide

Generally almost as efficient as Pt, and rather cheap, but labor intensive and somewhat problematic to coat a substrate with.

It is also mechanically fragile, has a non-negligible erosion rate, and it and its precursors are toxic compounds.

If I were going to use it, I suppose I would use it with a conducting substrate, and, rather than the hassle of spinning the substrate during the plating, I would use a surfactant. According to Wouter's page, Triton-X (which seems fairly cheap and readily available) won't work, but according to some patents I've seen, it supposedly does work.

As far as I'm concerned, the biggest drawback is the toxicity. I was actually preparing to use it, but I decided against it
as I just don't want the hassle of dealing with toxic lead compounds, especially the soluble precursors.

*****************************************

MnO2

There's not a lot of literature that I could find regarding this. The main problem seems to be the reliable formation of a
layer of beta-MnO2, vis-a-vis gamma-MnO2, which is inactive.

Supposedly the thermal decomposition of manganese nitrate leads to the beta form, whereas other precursors don't.

Also, in addition to erosion, I think I read where, depending on conditions, the beta form may slowly revert to the gamma
form over time. I'm not sure about this or about how much of a problem it really is in practice.

It would seem to be cheap and not very toxic (although manganese compounds can be neurotoxic if inhaled).

****************************************

Silicon

I found a patent that mentions its use as an anode for perchlorates, and a news group discussion where someone claims it worked, but that's all I could find. I would speculate that the difficulty of working with it may be one reason it apparently never became an important anode material.

****************************************

Graphite

This is probably the cheapest and easiest anode material to make *chlorates* with. According to what I've read in some
patents, getting a yield of 100 kg of chlorate will, depending on conditions, erode between 0.4 and 1.0 kg of material from an *untreated* graphite anode. If the graphite is impregnated with various resins to make it "waterproof", the loss can supposedly be reduced to 0.1 to 0.2 kg per 100 kg of chlorate.

Supposedly graphite will make perchlorate, although I've found hardly any documentation to that effect. I assume it will do so at low efficiency under relatively extreme conditions, e.g., low chloride and high chlorate concentration at higher voltage, compared to other materials.

In fact, if it is desired to make chlorate that is free from perchlorate contamination (especially in a "continuous"
process), graphite may be the material of choice, since all of the other materials seem to be much more likely to make
perchlorate under a given set of conditions.

I should say I have some ideas on how to treat graphite to make it better, and I'll probably post these ideas in the future.

*****************************************

"Mixed Metal Oxides"

This stuff, the active, outer layer of the so-called "Dimensionally Stable Anode" or "DSA", is looking pretty good to me.

After reading what I believe are the original two patents, and a few full text journal articles that I found on the internet, this seems the way to go for perchlorate production at home. (In fact the patent does recommend it for perchlorate production, but the recommendation is buried deeply within the body of the patent).

As I understand it, what has become known as a "DSA" has several distinguishing features of interest. The first is the
substrate of titanium or niobium for example, upon which an oxide layer is formed, I guess by anodizing. Regardless of
whether the next layer (the outer layer), is platinum, a single platinum group metal oxide, or mixed metal oxides, the point
is that intermediate oxide layer conducts current from the substrate to the outer layer, but doesn't conduct current to the brine. IOW, if the active outer layer gets dissolved in a spot, supposedly the intermediate oxide layer is a nonconductor, as far as the brine is concerned, and accordingly acts as a barrier to prevent the substrate from being corroded. So, rather than sudden catastrophic failure, the anode fails by the slow loss of active surface area as the outer layer erodes or dissolves or whatever it does.

Another feature is the use of metal oxides, rather than pure platinum, for example, as the active layer. Supposedly, when used in thin layers, the platinum group metal oxides are approximately as conductive as the pure metals themselves, while at the same time they are two orders of magnitude more resistant to corrosion by the brine and the electrolysis products. Moreover, ruthenium and palladium for example are much cheaper than platinum, so they are cheaper to make.

As I understand it, there is generally a platinum group metal oxide and a non platinum group metal oxide such as TiO2,
present in the outer layer. Although the anode would work without the TiO2 in the outer layer, it is better with it because it supposedly makes the RuO2 or PdO2 or whatever more chemically stable.

What I don't understand is why these "Dimensionally Stable Anodes" don't seem to be used in industrial perchlorate
production; or at least, why there's not much evidence that they are. This has me somewhat baffled.

In any case, it seems there are lots of companies out there using DSAs in pool chlorinators, an application for which they
seem to work very well. And the journal articles I found demonstrate that they work very well for chlorate production.

Since there seems to be many places selling generic DSA equipped pool chlorinator replacement cells, complete with anode, cathode and electrode terminals, I am probably just going to buy one of these to experiment with for perchlorate production.

Fleaker - 30-12-2005 at 19:49

Perhaps you should include titanium, which in many cases is as good an inert electrode as you can ask for.

jpsmith123 - 31-12-2005 at 06:43

Titanium is generally used as a cathode, or as an anode substrate; is this the use you had in mind?

Fleaker - 31-12-2005 at 10:42

Yes, I guess the key word would have been "electrode", my apologies for being vague. As a cathode it finds use in electrolysis and especially electroytic refining (i.e. gold refining) or as a substitue for nickel. I'm sure there are situations where it is not ideal, but I'm dragging this off topic

as I now see this is directed primarily towards the production of chlorates and perchlorates. However, I think this is a good idea jp, perhaps we should have discussion (or make a list of suitability or something like that) on cathodes and anodes.

12AX7 - 31-12-2005 at 21:29

FYI, titanium makes a nice diode: as a cathode, it passes current normally as any other metal. As an anode, no current flows.

You can probably develop colors (as Woelen with his niobium) by anodizing to various voltages in just about any acid solution.

Tim

jpsmith123 - 31-12-2005 at 23:41

Hello Fleaker,

Actually, my subject line should have been more specific.

What I'm interested in doing is tying up some loose ends (primarily involving anodes) regarding the home manufacture of chlorates and perchlorates, or at least, putting much of the relevant information in one spot, if possible.

I've found two or three dedicated web pages that relate to anodes, a few news group discussions here and there, and a few discussions in forums like this one, but none of what I've read so far has given me a warm and fuzzy feeling as to the best method of making perchlorates on a semi-serious scale at home.

I am leaning towards buying a replacement pool chlorinator cell and testing it for use in ClO4 production. Unfortunately, the cheapest one I found so far is almost $200 USD:

http://www.saltcells.com/ecomatic-sr75-generic-cell-p-481.ht...

I may also try to make one based on information in the attached patent.

As described in the patent, the inventor apparently even successfully treats a graphite substrate, creating a rugged RuO2-TiO2 coating that appears to hold up well in a subsequent test.

If this stuff can be slapped onto graphite (even if it doesn't last as long as a Ti or Nb substrate, who cares? if it's relatively cheap and easy to do) this may be the way to do it at home.

Unfortunately neither of the two patents I have go into detail regarding the tradeoffs among the various platinum group metal (PGM) oxides.

Ruthenium oxide seems to be an industry standard, but why, I wonder? Is it because it's somewhat cheaper?

From what I've read elsewhere, PdO may be the oxide of choice, at least in the sense that it generally has a low chlorine overpotential and a high oxygen overpotential, compared to the other PGM oxides; however this seems to be somewhat process dependent, mediated by both physical and chemical factors.

Pd compounds may also be less toxic than Ru compounds and somewhat easier to work with (although I think Pd oxidizes at a higher temperature compared to Ru).

Also, I don't know how the various PGM oxides compare in terms of general resistance to erosion under the conditions of interest.

If I understand correctly, the erosion occurs when small amounts of the oxides get reduced to metals, and that's supposedly why the mixture of oxides is needed - to stabilize the PGM oxide against reduction to the metallic state.

The (most likely small) differences in efficiency and ruggedness between Pd and Ru may be unimportant for a small scale home operation, with price, availability, toxicity and ease of use being more important.

Attachment: 3632498.pdf (830kB)
This file has been downloaded 2638 times

Another Patent

jpsmith123 - 31-12-2005 at 23:54

Attached is another related patent.

I guess it's too big...it didn't upload.

[Edited on 1-1-2006 by jpsmith123]

bio2 - 1-1-2006 at 02:12

....... regarding the home manufacture of chlorates and perchlorates, or at least, putting much of the relevant information in one spot, if possible............

Carbon cutting electrodes (gouging rods) used by welders work well. They are a bit soft and the copper coating needs removal but the price is right.

Using the 3/8 rods as both electrodes in a 8L chlorate cell produced a couple kilos
from NaCl in a 1 1/2 days leaving about half of the anode unconsumed. The small amount of carbon at the cell bottom did not interfere with the chlorates purification.

jpsmith123 - 2-1-2006 at 00:04

A few kilograms in 1.5 days? Wow...sounds like you were operating at a rather high current.

woelen - 2-1-2006 at 11:14

Quote:

Originally posted by 12AX7
FYI, titanium makes a nice diode: as a cathode, it passes current normally as any other metal. As an anode, no current flows.

You can probably develop colors (as Woelen with his niobium) by anodizing to various voltages in just about any acid solution.

Tim

It is a little bit off-topic, but I want to mention that I tried electrolysis of NaCl with an anode, made of titanium (I just purchased 2.4 meters of 1.5 mm thick 99.9% Ti-wire for EUR 5,-

). No current flows at all, when the voltage is below approximately 12V. The color of the wire shift from grey to a little brownish grey, but the color is not nice and bright as with the niobium experiments, it is more as if the wire is a little bit tarnished.

When the voltage is increased to 13V, the titanium anode dissolves/erodes, giving a white flocculent precipitate. When some dilute HCl is added, then this white precipitate does not dissolve. When some 3% H2O2 is added, then the white precipitate dissolves quickly, leaving a clear deep-orange liquid. This orange color is due to formation of a red peroxo-complex.

Summarizing, titanium is not suitable for production of chlorate, but that you all probably knew already

jpsmith123 - 8-1-2006 at 16:44

I'm wondering, is anyone else here interested in the idea of using a commercial (pool chlorinator) MMO anode (or complete cell) for ClO3/ClO4 production? I'm trying to get some prices, etc., from various manufacturers and/or distributors which I'll post here if there is any interest. If not, I won't waste bandwidth by posting it here.

Regards,
Joe

woelen - 8-1-2006 at 23:41

Yes, I'm interested in such anodes (not complete cells) if they are not too expensive. However, shipping may make things expensive (I'm in the Netherlands). But if you can obtain price info and find a supplier, who ships internationally, that would be very nice. I'm still looking for a good anode. Graphite is nice, but far from perfect.

jpsmith123 - 9-1-2006 at 05:34

I'm waiting for some info from a potential supplier right now. Unfortunately, most distributors seem to have little or no technical information at their disposal regarding chlorinator cells and electrodes.

I suspect that most manufacturers in fact use MMO coatings, but the use of imprecise language in a few instances, apparently by marketing people who don't know any better, forces me to have to ask each potential source.

As a last resort, I suppose the color of the anode may be a good indicator, since PGM oxides are essentially black, while the noble metals themselves wouldn't be.

In any case, I was originally considering buying a complete cell, but I decided against it as I believe that would be wasting money on a housing and possibly other hardware that I wouldn't use.

That's because pool chlorinator cells are designed for a relatively low salt concentration, so their electrodes are generally quite close together, to keep the voltage drop across the cell within reason when operating at the rated current.

Since I anticipate using saturated NaCl brine, and since since I'm not sure yet exactly what type of power supply I'll be using and exactly how I'll operate the cell, I think it would be best to have a setup with maximum flexibility.

Then there is also the issue of mesh vs. plate type anodes, and single plate vs multiple parallel plates. At this point, I'm leaning toward the single, relatively long plate, if for no other reason than that it should be easier to estimate current density, for purposes of fine tuning the process, e.g., when wanting to make high purity chlorate. The single plate type should also make it easier to adjust electrode spacing.

Pommie - 9-1-2006 at 06:53

I have a chlorinator cell on my pool. I could measure the voltage/current if it would be any help. It's supposed to produce 40g per hour of "active chlorine". This is attached to a 85000L pool and runs 8 hours per day to keep it bug free. The salt concentration is just tastable.

Anyway, if I can help in anyway then just ask.

Mike.

jpsmith123 - 9-1-2006 at 19:00

Quote:

Originally posted by Pommie
I have a chlorinator cell on my pool. I could measure the voltage/current if it would be any help. It's supposed to produce 40g per hour of "active chlorine". This is attached to a 85000L pool and runs 8 hours per day to keep it bug free. The salt concentration is just tastable.

Anyway, if I can help in anyway then just ask.

Mike.

Kindly remove the chlorinator and send it to me for testing ASAP

Seriously, thanks for the offer. You're in Australia? That (and also India) seems to be the land of pool chlorinators...you must almost be tripping over them...

I'm considering buying a "Sal-Chlor" generic replacement anode from one of the places in Australia. The only problem is that I have no official confirmation as of yet that it has a MMO coating.

I'm probably going to get one though, since the anode does appear to be black or nearly black from the picture I've seen.
Moreover, the price is right.

You don't perchance have a "Sal-Chlor" chlorinator, do you?

Axt - 9-1-2006 at 21:40

I have previously priced 1.5mm MMO (titanium substrate) electrode wire which ran ~$8 AUS (~$6 US) per metre. Though minimun order of 25m

The wire was meant for cathodic protection of steel structures. Possibly a better (cheaper) source then pool chlorinators. They are available in ribbon/plate/mesh etc. I think there is also Ti/Cu alloy substrate.

[Edited on 10-1-2006 by Axt]

jpsmith123 - 10-1-2006 at 00:50

Hmmm, I can see possibilities there. Thanks for that info, Axt. Does this supplier have a web site?

Axt - 10-1-2006 at 02:04

Yes, the Australian manufacturer/supplier is nmtelectrodes.com, though I expect that there is suppliers world wide search for "ICCP electrodes" ( for Impressed Current Cathodic Protection) or words to that effect.

chemoleo - 10-1-2006 at 03:47

I am not sure if this has been mentioned before; forgive me if this was already considered a long time ago.

Why not just using PbO2-coated lead plates from old car batteries? They are exactly what we want. Why all the hassle of coating, if they are freely available in old batteries?

Axt - 10-1-2006 at 03:55

Battery electrodes have an exposed lead mesh substrate, they fall to bits fast.

chemoleo - 10-1-2006 at 04:21

And what if they are very loosely held in place with a very very restricted amount of polyester-like hardener? I am sure this could be made to work, if this is the only problem!?!

Axt - 10-1-2006 at 04:44

They are a rectangular lead mesh with pressed PbO2, the lead is not completely covered in PbO2, nor is the PbO2 impervious to liquids. The lead will quickly corrode away. I dont think there is any way they could be made practical.

Below is a plate from a car battery, see the exposed lead around the edge and along the mesh.

<center><img src="http://www.sciencemadness.org/scipics/axt/battery-electrode.jpg"></center>

jpsmith123 - 10-1-2006 at 05:22

Unfortunately it seems many people have already tried using lead-acid battery anodes, all unsuccessfully, AFAIK.

Here's a thread which describes what is probably a typical example:

http://www.sciencemadness.org/talk/viewthread.php?
tid=1425

MMO based anodes seem to be one approach that hasn't been fully explored, or at least documented, IMHO.

Since it seems that 15 or 20 amp rated MMO coated Ti anodes can be had for $75 to $100 USD, I think it's worth trying.

If they turn out to be as good for home ClO4 production as it seems they should, then it might be interesting and maybe even economical to try to coat Ti substrates at home.

Especially if the info like the following from the patent I uploaded is accurate.

***************************************

Example XVI

Two titanium rods were degreased and pickled and subsequently placed in a galvanic bath having the following composition:

100 cc. ethanol
100 cc. water
1 g. ruthenium chloride
10 g titanium chloride

and subsequently connected to a source of alternating current of 13 volts and a current density of 15 amp/m^2, temperature 20-30 degrees C., for a period of about 20 minutes.

After about 20 minutes both rods were coated with a mixture of titanium oxide and ruthenium oxide, the adhesion of which was still further improved by heating at 400 degrees C for 5 minutes.

The anode thus made is excellently suitable for use in various electrolyses at low current densities.

chemoleo - 10-1-2006 at 05:25

Ok- well at least in Germany, car batteries are (were?) definitely not made of a mesh-material. They were solid, and I know this because I took them apart.

Regardless- I was wondering, what evidence is there that the lead will quickly corrode away?? After all, it'd be covered with PbCl2, which is quite insoluble, or simply with more PbO2. Alternatively, one could i.e. add a small amount of Na2SO4 to the NaCl solution (which is what the electrolyte is, NaCl, NaOH, NaOCl, and NaClO3), which would cover any free Pb.

Hmm. Did you try this very thing, using battery electrodes, and did you find corrosion that made the system unworkable?

Nonetheless, I can see the following solutions - dip the mesh into NC-acetone lacquer, let it soak. Take it out to dry. Then dip it into acetone again, just to remove the OUTER layer of NC, and let it dry again. A significant amount of PbO2 should be exposed now, no? Or something along those lines. Anyway. This probably belongs to the dedicated PbO2 thread, might merge it there later.

chloric1 - 10-1-2006 at 06:35

Somewhere I heard of an older patent from 1977 that takes titanium and coating this with SnO2 with some MoOx and finally ruthenium oxide. All steps incorpate a volatile salts and application of heat of 600 to 800 C to decompose tho the oxide. So possibly pickling titanium in wamr oxalic acid, brushing on concentrated stannous chloride solution and applying a flame to decompose to SnO2. Follow this with Ammonium Molybdate solution and ruthenium trichloride. The ruthenium salts will be difficult because the carbon monoxide from the flame would reduce it to the metal. An electric oven is needed here.

jpsmith123 - 10-1-2006 at 06:58

I have to say I didn't try anything with lead.

I was preparing to do so, but then decided that, given the apparent lack of evidence of success by others who've tried it, and the hassle of dealing with the toxicity of the stuff, I decided it's best to try MMO type anodes first; since they are not only commercially available at moderate cost, but since they are supposed to hold up so well.

If the MMO anode doesn't live up to expectations, I'll probably pick up where I left off with the PbO2.

12AX7 - 10-1-2006 at 09:15

I tried a bar of lead, and posted about it. Basically, at low temperature, it passivates with PbCl2, which then slowly oxidizes to a flakey PbO2/PbCl2 deal. In hot brine, it works pretty reasonably to corrode the lead to Pb(OH)2, as you would expect from the solubility of PbCl2.

Tim

This is getting to be a major PITA.

jpsmith123 - 12-1-2006 at 21:50

I thought it would be relatively easy to find an affordable MMO pool chlorinator anode. Not so, in my experience so far...shrug...

Part of the reason for getting one is to answer the question of just how well MMO anodes make ClO3 and ClO4, how well they hold up, and to document the results.

In order to do that in the most meaningful way, I need to know as precisely as possible just what type of coating I'm using...and therein lies a big problem.

Most of the relevant patents seem to have expired, and now it's a big free-for-all out there...everything's apparently a "trade secret".

There's a big bunch of OEM's making pool chlorinators, and perhaps an even bigger bunch of manufacturers making "generic" replacement cells for them.

So you have all kinds of different coatings, i.e., different combinations of PGMs and PGM oxides alloyed with "film forming metal" oxides, etc., and different manufacturing processes used to apply the coatings.

Just for asking one of the OEMs about their coating, I've basically been accused of being an industrial spy...needless to say they gave me no information.

Anyway, I was laboring under the impression that any black or nearly black coating implied at least a PGM oxide coating...but then I discovered something called "black ruthenium" plating, which is black and which is ruthenium but which is apparently not an oxide, and at least one vendor selling an anode with a black coating claims his coatings are plain ruthenium. Another claims to be using pure iridium. Unfortunately I could find no useful information regarding "black ruthenium" or similar types of plating.

So now, rather than getting the cheapest anode or what may be the best type, i.e., single plate vs multiple plates vs mesh, it looks like I may go with the one for which I get the most detailed and reliable information regarding the coating, to the extent that's even possible in the first place.

Update: Apparently all the generic replacement cell products at saltcells.com have ruthenium oxide type MMO coatings. So I am leaning once again toward the generic "sal-chlor" anode.

[Edited on 13-1-2006 by jpsmith123]

Ordered An Anode Today

jpsmith123 - 16-1-2006 at 01:57

For the few that may be interested, today I ordered an anode (actually I ordered the anode, cathode and insulators - the whole cell minus the housing). The price for the cell parts was about $130.00 AUD, and international shipping was $25.00 AUD; the total cost in U.S. dollars was about $118.00.

The parts are for a generic Sal-Chlor 12" cell from the following vendor:

http://www.directpoolsupplies.com.au/prod646.htm

The cell has a titanium plate anode (hopefully with MMO coating) and a titanium mesh cathode.

I probably won't receive it for a few weeks, but once I get it running I'll report on how it performs.

Finally Received The Chlorinator Cell Assembly

jpsmith123 - 5-2-2006 at 23:56

In case anyone's interested, the cell assy. arrived a few days ago.

I'll try to attach a picture of it.

Unfortunately the anode is not a solid plate, as I expected, but a "mesh plate". It should still work, but it will be more work to figure out exactly what the working surface area is.

Both the MMO coated titanium mesh anode and the titanium mesh cathode are spot welded to titanium brackets that serve as electrical contacts.

The next problem is to find a suitable cell body, which will need to be at least about 14 inches deep.

Cell Assembly.jpg - 57kB

garage chemist - 15-2-2006 at 10:13

Look what I found while searching for something different!
An article about the different types of Ti/noble metal anodes used in chlor-alkali and chlorate manufacture.
Note that they cannot be used to directly make perchlorates from chlorides.
To make perchlorates, chloride- free NaClO3 must be prepared first and this then electrolyzed in a separate cell.

http://docserver.ingentaconnect.com/deliver/cw/matthey/00321...

[Edited on 15-2-2006 by garage chemist]

jpsmith123 - 15-2-2006 at 15:18

The link does not work for me garage chemist. Can you upload the paper?

garage chemist - 15-2-2006 at 15:25

It doesn't work for me any more too... I'll try to fix it.

[Edited on 15-2-2006 by garage chemist]

jpsmith123 - 15-2-2006 at 15:30

Maybe you could split it into 2 pieces (if you have Adobe Acrobat)?

Or can you post a link to the site and I'll search for it? Thanks.

garage chemist - 15-2-2006 at 15:31

Here is a working link, click on the pdf button:

http://www.ingentaconnect.com/content/matthey/pmr/1998/00000...

jpsmith123 - 15-2-2006 at 15:57

Thanks. Interesting historical perspective on the development of DSA anodes, but I didn't see anything about perchlorate production...only chlorate. Did I miss something?

garage chemist - 16-2-2006 at 09:01

Those are the anodes that are used in pool chlorinators. I think you know them better than me since you surely did a lot of reading and literature research before spending such an amount of money on one.

Anyway, perchlorates can also be conveniently made from chlorates by thermal decomposition, I've done it and the yields were rather good.
Best way is still electrolysis of chlorates with platinum anode. My platinum anode cost me only ca. 30€, since I made it myself from Pt wire (hint: use 0,5mm diameter, they are the most economic. 0,3mm is too thin for most cells, although I had my first succes with it. It just takes longer since the maximum current you can put through them is 2 A ).

[Edited on 16-2-2006 by garage chemist]

Gouging rods

MadHatter - 17-2-2006 at 08:43

JP, the treatment for gouging rods involves peeling off the copper plating and then soaking
in linseed oil. This slows the erosion in the cell. I made 8 LBS of KClO4 using gouging rods.
It's a matter of technique. Keep the cell temperature below 40 C and the erosion proceeds
at a much slower rate. Use a cut up steel can for the cathode and don't worry about
the iron hydroxide that forms because the fluffy white shit is so insoluble that it, along with the
carbon bits filter out readily. I bend the steel to make an inverted V shape and the gouging
rod sits directly below it. This way, the rising chlorine runs into the hydroxide formed at the
cathode. My cell has a 5 litre volume.

[Edited on 17-2-2006 by MadHatter]

garage chemist - 17-2-2006 at 09:01

You mean those, right?
http://cgi.ebay.de/10-COPPER-CLAD-CARBON-CUTTING-RODS-NOS_W0...

They seem to be totally unknown in germany. I've never found any of them anywhere. I'd like to get some, since I could use them for maing bromates (chlorates and perchlorates I already have enough).

Gouging rods

MadHatter - 17-2-2006 at 09:16

Yes that's what I mean. Do you have a welding supply shop close to you ? That eBay price is
way too high ! I paid 26 USD for a box of 100 of these !

jpsmith123 - 17-2-2006 at 22:24

Garage Chemist,

If I remember correctly, your perchlorate production started with NaClO3 (OTC as weed killer?); I'm wondering, did you do a batch type process, or did you do a continuous process whereby you continually add chlorate and your NaClO4 precipitates out? And how did your Pt wire anode hold up?

I plan on first making chlorate, and then using that in a separate run to get perchlorate. (BTW it seems that in order to get maximum energy efficiency and minimum anode wear (at least for platinum anodes) the best method, for either chlorate or perchlorate production, would be a "continuous" process; see e.g., US Patent #5004527).

As of right now I will be using a pyrex 1L graduated cylinder as a cell body. I found an old 5 volt 15 amp power supply laying around that I hope will suffice...maybe sometime next week I'll be able to start experimenting with it.

MadHatter,

I'm impressed that you were able to practically make useful amounts of KClO4 with graphite anodes. (I may try it one of these days as I found some 3/8" x 12" graphite rods lying around here - they're marked "National Intensiarc" - they look like gouging rods but they have no copper coating).

Anyway, I'm wondering, what kind of material did you use for your cell body?

garage chemist - 18-2-2006 at 02:59

For cell body I used glass, a 250ml jar with screw-lid where the electrodes and gas exhaust were installed.

I used OTC (well, not in germany, but in France at that time- nowadays very hard to find even there) sodium chlorate solution (45% strength). It is completely chloride- free as a test with AgNO3 solution showed, and this is also important for minimizing anode erosion.

2-4 g/L of potassium dichromate must be added to this in order to prevent reduction of chlorate at the cathode, which would produce chloride and cause anode erosion.

The cell liquor must be magnetically stirred, as proper mixing is very important.

The power supply must be of the type with adjustable current limiting, otherwise you won't be able to keep a constant current.
And 15 A are WAY too much. For a 250ml cell, 2 A are good and 4 A the absolute maximum when used with a cooling bath.
A 0,5mm Pt wire is also not to be used with more than 4 A, or the solder connection will de-solder itself.

The maximum current that can be run through the cell depends firstly on the anode and secondly on the cooling and therefore on the surface of the cell body that touches the cooling bath, and also on the thickness on the glass. Do not let the temperature rise above 40°C.

The progress can be nicely observed by watching the anode.
At the beginning, there will be only very slow oxygen evolution, as that oxygen goes into oxidation of the chlorate.
When there is only little chlorate left to oxidise, the oxygen production increases, and an ozone smell can be noticed, which gets more and more intense as the chlorate is used up.
When nearly all chlorate is gone, there will be strong oxygen/ozone evolution and all energy now goes into splitting of the water.

I connect the exhaust of my cell (connection must be airtight, of course) to a wash bottle filled with water which serves as a bubble counter.
At the beginning, only hydrogen flows through it and the gas evolution is measured by counting the bubbles in a time span of, say, 30 seconds. When the chlorate is used up, the gas evolution will have increased by 50% and the gas consists of a perfect hydrogen/oxygen mix which can be collected in an inverted test tube and ignited FAR AWAY from the cell. It will explode with a loud bang, opposed to the very light puff that the pure hydrogen at the beginning of the electrolysis makes.

To oxidise 1 mol of chlorate into perchlorate, 2 mol of electrons are needed. 1 mol of electrons is 26,8 Ah.
Calculate the required ampere hours and run at least the double amount of this through the cell.

When the cell is done, I have a ca. 50% NaClO4 solution (NaClO4 is very soluble and cannot be crystallized easily, so it is a batch- wise process).

I destroy residual chlorate by acidifying the solution, adding sodium disulfite and boiling. The solution must give off SO2, otherwise more disulfite must be added. A SO2 smell from the solution is the sign that all chlorate has been reduced.
This also reduces the added dichromate to trivalent chromium, which is then precipitated as the hydroxide by adding NaOH solution and filtering.

From this I can make KClO4 by adding KCl solution (precipitate is very fine and difficult to filter and must always be recrystallized from boiling water to make larger and purer crystals), or ammonium perchlorate (saturated NH4NO3 solution is needed for this, and NH4Cl is not soluble enough so that the yields will be low if you use this). For ammonium perchlorate, strong cooling is necessary since it is quite soluble at ambient temperature.
Yield of KClO4 calculated from NaClO4 is often as high as 90- 95 %, even after recrystallization (at 0°C it is realy very sparingly soluble which explains the good yields).
For ammonium perchlorate yields are about 50%.

A perchlorate cell is much cleaner to operate than a chlorate cell, but the parameters temperature, current density at the anode and composition of the electrolyte must be closely controlled for it to work. If this is done, then a perchlorate cell is often much more efficient than a chlorate cell.

[Edited on 18-2-2006 by garage chemist]

jpsmith123 - 18-2-2006 at 06:24

Quote:

For cell body I used glass, a 250ml jar with screw-lid where the electrodes and gas exhaust were installed.

What was the lid made out of?

Quote:

2-4 g/L of potassium dichromate must be added to this in order to prevent reduction of chlorate at the cathode, which would produce chloride and cause anode erosion.

I'm trying to get some persulfate for this purpose. If I can't find any I'll just have to get along without it.

Quote:

The cell liquor must be magnetically stirred, as proper mixing is very important.

I'm hoping that, with the setup I have, the hydrogen evolution from the cathode will result in enough stirring.

Quote:

The power supply must be of the type with adjustable current limiting, otherwise you won't be able to keep a constant current.

For the way I plan on operating the cell, i.e., in a "continuous" manner, I'm thinking that the resistance won't fluctuate too drastically.

Quote:

And 15 A are WAY too much. For a 250ml cell, 2 A are good and 4 A the absolute maximum when used with a cooling bath.

Well 15 amps is the max output capacity of my power supply...I don't necessarily intend to run at that current.

Quote:

A 0,5mm Pt wire is also not to be used with more than 4 A, or the solder connection will de-solder itself.

For now I'll be using the MMO pool chlorinator anode, which supposedly can handle lots more than 4 Amps, but I plan on not being very aggressive, at least until I get a feel for what's going on.

Quote:

The maximum current that can be run through the cell depends firstly on the anode and secondly on the cooling and therefore on the surface of the cell body that touches the cooling bath, and also on the thickness on the glass. Do not let the temperature rise above 40°C.

I'll be using a 1 L pyrex graduated cylinder, which is relatively long and narrow and should therefore make for efficient cooling; i.e., hopefully the radial temperature gradient will be small.

Quote:

The progress can be nicely observed by watching the anode.
At the beginning, there will be only very slow oxygen evolution, as that oxygen goes into oxidation of the chlorate.
When there is only little chlorate left to oxidise, the oxygen production increases, and an ozone smell can be noticed, which gets more and more intense as the chlorate is used up.
When nearly all chlorate is gone, there will be strong oxygen/ozone evolution and all energy now goes into splitting of the water.

I connect the exhaust of my cell (connection must be airtight, of course) to a wash bottle filled with water which serves as a bubble counter.
At the beginning, only hydrogen flows through it and the gas evolution is measured by counting the bubbles in a time span of, say, 30 seconds. When the chlorate is used up, the gas evolution will have increased by 50% and the gas consists of a perfect hydrogen/oxygen mix which can be collected in an inverted test tube and ignited FAR AWAY from the cell. It will explode with a loud bang, opposed to the very light puff that the pure hydrogen at the beginning of the electrolysis makes.

Sounds like a clever idea...watching for increased gas evolution that way...to determine when to harvest the ClO4.
Some people claim that they wait until they smell ozone, but if I were to do a batch process, I think I'd rather have a visual indication.

Quote:

When the cell is done, I have a ca. 50% NaClO4 solution (NaClO4 is very soluble and cannot be crystallized easily, so it is a batch- wise process).

I'm hoping that by continually adding NaClO3, the NaClO4 will precipitate out.

Quote:

I destroy residual chlorate by acidifying the solution, adding sodium disulfite and boiling. The solution must give off SO2, otherwise more disulfite must be added. A SO2 smell from the solution is the sign that all chlorate has been reduced.

I'm hoping that a continuous process will lead to a fairly pure product, but I have a supply of Na2S2O5, so that's what I'll do if need be.

Quote:

From this I can make KClO4 by adding KCl solution (precipitate is very fine and difficult to filter and must always be recrystallized from boiling water to make larger and purer crystals), or ammonium perchlorate (saturated NH4NO3 solution is needed for this, and NH4Cl is not soluble enough so that the yields will be low if you use this). For ammonium perchlorate, strong cooling is necessary since it is quite soluble at ambient temperature.

In my case, I want at least some of the perchlorate as NaClO4. Have you ever recovered and kept any solid NaClO4, or did you immediately go from liquor to KClO4?

BTW, I'm curious, how well is your Pt anode wire holding up?

garage chemist - 18-2-2006 at 07:12

The lid was the ordinary plastic coated metal lid it came with (it originally contained tomato sauce

).
The connections and exhaust were fitted into the lid by drilling holes and using silicone. This worked well.

Make yourself some potassium dichromate, it's very easily made from Cr2O3 (available at art supply stores). Go to frogfot's site for a detailed synthesis.

And the hydrogen evolved will NOT result in satisfactory stirring. Use a magnetic stirrer, it can be as simple as a magnet on a motor under the cell and a steel bar coated with plastic or sealed into a glass ampoule inside it.
Otherwise acidic layers will develop around the anode and attack it.

You cannot precipitate NaClO4 by adding anything, it is far more soluble than NaClO3! Even boiling down the cell liquor to half its volume and cooling won't make any solid NaClO4.
I use my NaClO4 as the 50% aqueous solution I get by destroying the chlorate and precipitating the chromium, the only impurities are sodium sulfate, sulfite and chloride when HCl is used for acidification.
For all reactions using it it has to be dissolved anyway, so it would be a waste of time to isolate the solid salt, which is a real pain. I speak from experience (boiling down the solution will make a thick sludge from which no crystals can be obtained).

NaClO4 cannot be obtained in a continous process, as it can't be separated from the solution.
It is produced as the 50% solution in water which can be used for all desired purposes.

If the cell is operated correctly, the Pt wire is not visibly attacked.
The only time it got attacked was when I ran the cell without dichromate.
After this, the cell also contained some chloride due to reduction of chlorate at the cathode.
Persulfate will not prevent this. For platinum anode, dichromate has to be used.
It forms a diaphragm of hydrous chromium oxide around the cathode, preventing the contact of nascent hydrogen with the electrolyte.

[Edited on 19-2-2006 by garage chemist]

Perchlorate

MadHatter - 18-2-2006 at 10:53

1st, I need to correct an error I made on the gouging rods:
That was 26 USD for 50 - not 100. My apologies. Still thats only 52 cents a rod.

My cell body is basically a 5 litre glass cookie jar that I found at Walmart. I like the V-shape
cathode because the chlorine or oxygen rises from the anode to mix with cathode
products. This is why I don't need to stir. The worst possible configuration for the
electrodes is to have them sitting on opposite sides of the cell. Very little mixing occurs.
As mentioned before, keeping the cell temperature below 40C(104F) keeps the rate of
erosion down.

Solubilities for compounds from CRC 62nd Edition(1981-1982), grams per 100ml H2O:

KClO4 .75 @ 0C 21.8 @ 100C
NaClO4.H2O 209.0 @ 15C 284.0 @ 50C

I start my electolyte at 9% by weight KCl. A little NaCl is mixed in because oxidation
of NaCl is more efficient than KCl. The metathesis reaction with KCl forces KClO4 out of
solution because of its much lower solubility. I put 2g of NaF in the electolyte to improve
current efficiency. Voltage is at 6 and amps are adjusted to keep the cell temperature
below 40C. After completion, FeSO4 is used to destroy any residual chlorate. The rest is
fractional crystallization to get the KClO4.

jpsmith123 - 18-2-2006 at 22:22

Quote:

The lid was the ordinary plastic coated metal lid it came with (it originally contained tomato sauce

).
The connections and exhaust were fitted into the lid by drilling holes and using silicone. This worked well.

I was wondering how well silicone adhesives hold up to the brine. I'm glad to hear it works.

Quote:

And the hydrogen evolved will NOT result in satisfactory stirring. Use a magnetic stirrer, it can be as simple as a magnet on a motor under the cell and a steel bar coated with plastic or sealed into a glass ampoule inside it.

Since I have little relevant literature and I have yet to make any ClO4 myself, I can't really agree or disagree with you. I do know that other people have made ClO4 without additional stirring...whether or not they paid a significant penalty in terms of low efficiency or anode wear, I don't know.

I wonder if air bubbled in from an aquarium air pump would help?

Quote:

You cannot precipitate NaClO4 by adding anything, it is far more soluble than NaClO3! Even boiling down the cell liquor to half its volume and cooling won't make any solid NaClO4.

Since the solubility of NaClO4 although relatively high is nevertheless finite, I would guess that getting it out of solution is possible.

Quote:

I use my NaClO4 as the 50% aqueous solution I get by destroying the chlorate and precipitating the chromium, the only impurities are sodium sulfate, sulfite and chloride when HCl is used for acidification.
For all reactions using it it has to be dissolved anyway, so it would be a waste of time to isolate the solid salt, which is a real pain. I speak from experience (boiling down the solution will make a thick sludge from which no crystals can be obtained).

NaClO4 cannot be obtained in a continous process, as it can't be separated from the solution.
It is produced as the 50% solution in water which can be used for all desired purposes.

I almost hate to speak on the issue, since I've yet to try it myself, but others are claiming it's possible. One person who's made a few posts here, "gilbert pinkston", has claimed he got NaClO4 crystals directly from his electrolysis cell...and he's provided pictures, which I will try to attach.

Quote:

If the cell is operated correctly, the Pt wire is not visibly attacked. The only time it got attacked was when I ran the cell without dichromate. After this, the cell also contained some chloride due to reduction of chlorate at the anode.

I think you meant to say that the reduction would occur at the cathode?

Quote:

Persulfate will not prevent this.

You may be correct, however it is purported to enhance efficiency, and I assumed the mechanism would be by way of prevention of the reduction of chlorate.

[Edited on 29-10-2008 by chemoleo- resized pic]

[Edited on 29-10-2008 by chemoleo]

NaClO4_crystallized.jpg - 67kB

garage chemist - 19-2-2006 at 00:14

Of course I meant reduction at the cathode. what a stupid typo!

I haven't treid persulfate, but I don't want to attack the platinum another time, so I keep on using dichromate from which I know it works.

That crystallized NaClO4 looks interesting. That solution must be at ca. 70% concentration for this to occur (solubility 200g/100ml water at 0°C). And only a small portion of the NaClO4 will crystallize. The solubility is really extremely high!

For a continuos process, you can elctrolyze a KClO3 solution (easier to make and purify than NaClO3 due to stronger temperature dependence of solubility) at 0°C.
The formed KClO4 will directly crystallize at the anode and fall down to the bottom. After no more KClO4 is formed, the solution can simply be filtered or decanted and re-saturated with KClO3.
An improvement of this process would be to hang a cotton bag filled with solid KClO3 into the elctrolyte to replenish KClO3 in the elctrolyte at the same rate as it is used up. This would need some stirring, of course.
The obvious disadvantage of this process is that only KClO4 can be made like this.

Stirring with air blown in by a pump would be a good idea, I think this would suffice for efficient stirring in a perchlorate cell. This technique is known as air stirring and is used for the stirring of nitroglycerine batches (to minimize mechanical shock).
It would be a good substitute for magnetic stirring.
Of course this means that you can't measure the gas evolution any more, but it isn't really important.

MadHatter, did you make it from chloride directly to perchlorate with only graphite? That's very remarkable. The low temperature and low current density in your cell has apparently largely prevented erosion of the graphite.
But the current efficiency must have been really low, since chlorate cells need high temperature for high efficiency (but high temperature also favors erosion of the graphite...).
But they work with low temperature, too. The chlorine dissolves even better at low temp, so the pH would have to be adjusted less often than with a hot cell.

[Edited on 19-2-2006 by garage chemist]

[Edited on 19-2-2006 by garage chemist]

jpsmith123 - 19-2-2006 at 08:21

Quote:

That crystallized NaClO4 looks interesting. That solution must be at ca. 70% concentration for this to occur (solubility 200g/100ml water at 0°C). And only a small portion of the NaClO4 will crystallize. The solubility is really extremely high!

Well I don't know exactly how he operates his cell, but my guess is that he starts with highly concentrated NaClO3 solution, maybe he adds some additional NaClO3 to the cell as the electrolysis proceeds, in order to build up a highly concentrated NaClO4 solution, and then at some point he turns off the power and adds more NaClO3, which, by way of the common ion effect, will cause an appreciable amount of the NaClO4 to precipitate out. And then the cell is already prepared for another run.

Quote:

For a continuos process, you can elctrolyze a KClO3 solution (easier to make and purify than NaClO3 due to stronger temperature dependence of solubility) at 0°C.
The formed KClO4 will directly crystallize at the anode and fall down to the bottom. After no more KClO4 is formed, the solution can simply be filtered or decanted and re-saturated with KClO3.
An improvement of this process would be to hang a cotton bag filled with solid KClO3 into the elctrolyte to replenish KClO3 in the elctrolyte at the same rate as it is used up. This would need some stirring, of course.
The obvious disadvantage of this process is that only KClO4 can be made like this.

I was considering some kind of bag to hold the chlorate (or chloride, as the case may be). I was thinking maybe some kind of PVC mesh. Will cotton hold up?

KClO4

MadHatter - 19-2-2006 at 08:34

Garage Chemist, that's one tip I hadn't thought about - using an air pump(aquarium)
to achieve the stirring effect. Easier to setup than a magnetic stirrer. Thanks !

Websites that can help:

Wouter: http://www.wfvisser.dds.nl/EN/kclox_EN.html
Cape Canaveral: http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

Perchlorate production begins when the chloride(by weight) drops below 10%. This is why I
start my electrolyte at 9% to get things going immediately. I have to replace the gouging rods
a few times during the process but that's fine with me because they're cheap to use.
8 LBS of KClO4 for about 3.12 USD(6 rods) is bargain IMHO. I still have almost 90 rods left.
A few were consumed early on while tweaking the technique and of course producing
straight chlorate using saturated KCl solutions. The lovely cactus needle like formations
are indications that the chlorate is being produced.

Dichromates, fluorides, and persulphates are used to increase the efficiency of the operation.
I've used all 3 at different times. Personally, I like NaF. It works very well and it's cheap.
As for cathodic protection, I couldn't give a damn. I'm not worried about consuming a
soup can.

I haven't had much time lately to experiment with anodes but I do have the dioxides of lead,
manganese, and titanium to work with. I also have about 2 meters of titanium rod to use as
a substrate for coating lead dioxide(from the acetate plating bath) to work with. The problem
is getting a thick enough coating of PbO2 onto the Ti so it won't be attacked during the
electrolysis.

[Edited on 19-2-2006 by MadHatter]

jpsmith123 - 19-2-2006 at 08:51

Quote:

Originally posted by MadHatter
Garage Chemist, that's one tip I hadn't thought about - using an air pump(aquarium)
to achieve the stirring effect. Easier to setup than a magnetic stirrer. Thanks !

Hey, that was my idea!

BTW MadHatter, do you remember what kind of anode current density you were running to make your KClO4?

Air pump

MadHatter - 19-2-2006 at 09:32

JP, sorry ! I should have given credit where it was due ! My sincerest apologies !

I like to have .2 amps per square centimeter on the anode. That's about 7 amps on a 3/8"
by 12" gouging rod. I keep the voltage at 6.

FrankRizzo - 19-6-2006 at 20:09

jp,

Any new devolpments on using your chlorinator anode?

jpsmith123 - 20-6-2006 at 02:31

For a cell body, I used a 1 L pyrex graduated cylinder, and for a lid, I used a slightly modified plastic lid from a jar of Skippy peanut butter, which held the electrode assembly.

The disadvantage of the "Salchlor" anode is the length; at 12 inches long, it is hard to find suitable containers that can accomodate the whole electrode. In retrospect, I think it would have been better to go with the "Autochlor" AC-20 or AC-25 chlorinator cell assembly.

Anyway, I filled the cell with saturated NaCl solution and ran about 15 amps through it, but it made more chlorine gas than I was expecting, and I was afraid it would bother the neighbors, so I shut it down

.

I decided to put the project temporarily on hold, as I don't really have a good place to work right now. Hopefully, in a few more weeks, that situation will change, and I'll be back in business.

(In the meantime, apparently someone on the E&W forum has used a pool chlorinator anode similar to mine, to make a few lbs. of NaClO4, apparently in a batch type process. I'm thinking maybe someone registered on both forums can ask that poster for the specifics of his cell arrangement and process and post any useful information here).

The_Davster - 21-6-2006 at 18:08

You can reduce the chlorine by wrapping the anode down into the electrolyte a little way with teflon tape. This way the chlorine has more time to react with the NaOH in the solution. I have done it with electrical tape, it held up rather well.

Has anyone ever experienced a chlorate cell's resistance increasing as it runs? Sunday I started a run, it was pulling 11A, monday 9.5, tuesday,7.5, wednesday, 6. It is a 500ml cell, platinum anode, platinum and graphite cathode. Calculating the run time is going to be a bitch this way, as I only check the thing twice a day.

Also, does anyone know anything about the use of niobium for anode material. If I try hard enough(read:begging) I may be able to get some niobium tubing.

EDIT: I meant anode, not cathode for the niobium.

[Edited on 22-6-2006 by rogue chemist]

Resistance

MadHatter - 22-6-2006 at 09:28

Yes, I've noticed that current drops as the heat rises in the cell. With the gouging rods I
keep the cell temperature below 40 C(104 F). I supervise my runs and when 40 C is
reached I turn off the power supply to let it cool. This reduces the anode erosion.

I don't know that niobium will make any difference as a cathode. I've used steel, gouging
rods, and titanium tubing - all with good results. The anode is the critical component. The
Salchlor anode uses precious metals(not listed on their website) on a titanium substrate.
I figured it had to be something like that because the EPA and the medical community would
totally freak out if lead dioxide was used.

jpsmith123 - 22-6-2006 at 12:32

I got a "generic" Salchlor replacement cell, as the generic replacement cells seem to be generally cheaper than the OEM products.

I did ask Salchlor (the OEM) what the coating is on their anodes, but they refused to tell me, apparently thinking I'm an industrial spy or something. (In fact, the person I corresponded with was downright nasty).

Anyway, I believe the anode coating is a MMO coating, and one place told me it was iridium [oxide] and another told me ruthenium [oxide], so I'm not 100% sure what it is, exactly, but I believe all the PGM oxides are essentially in the same ballpark regarding performance.

The_Davster - 22-6-2006 at 14:54

Oops, meant anode, not cathode.

Anyway, I think part of the reason that the resistance was increasing was because the electrode connections were oxidizing. The .4 mm platinum gets quite hot with the lots of amps, and it turned the copper wire connectors into CuO slowly. After cleaning it I am back up to 7.5A ish. That still does not explain the rest of my amperage loss.

My runs are pretty much unsupervised, just top up the cell every day with salt solution, add ice to the cooling bath, and perhaps mess with the mag stirrer speed. I think I usually run at 80-90 degrees. Too hot to touch the 500ml flask for sure!

jpsmith123 - 22-6-2006 at 15:05

Rogue Chemist,

I'm curious, are you after chlorate or perchlorate, and are you trying to do a batch process or a continuous process?

The_Davster - 22-6-2006 at 16:07

Just a batch of chlorate.

But What I was pondering if niobium could be used as the anode is that a cell could be constructed with both electrodes hollow, so that water could be pumped through as coolant for the cell. By use of a pump a thermostat could control the pumps power keeping the cell at a specific temp. The electrodes being directly cooled would also stop a problem(which I forgot what it was) that is a result of the electrodes being too hot.
I don't have the electronics knowledge or desire for large ammounts of chlorate to really do lots of work on this.

12AX7 - 22-6-2006 at 18:18

Niobium, like titanium and similar metals, anodize. Should work fine as an overkill cathode.

Niobium can be plated with PbO2, right?

Tim

Lead plates for electrode??

gregxy - 28-6-2006 at 09:57

Has anyone tried using lead plates for the anodes in chlorate cells? Before making the chlorate you would fill the cell with dilute H2SO4 and run it for a few hours to generate a PbO2 coating over the lead anode.

I tried taking apart a UPS battery. Both the anode and cathode are made of a spongy type of lead. They probably make them this way to maximize the surface area. Unfortunately this also make them very fragile and chunks of the spongy oxide are prone to break off. For chlorate cells we don't need this high area anyway.

Simple sheets of lead say 0.125" thick might work better. The only question is if the oxidation stops once a coating is generated or if it keeps on going until the entire lead plate is consumed. I guess this would be determined by the permiablity of the oxide. However most metals stop oxidizing once that a suitably thick insoluable oxide has developed.

12AX7 - 28-6-2006 at 14:02

Read the PbO2 thread. I tried electrolysis of NaCl and lead anode. I also tried anodizing it with sulfuric acid first, producing a stronger but nontheless stressed anode which breaks up after a while.

Tim

gregxy - 29-6-2006 at 09:32

I read all of those threads. Everyone tried electrodes from car batteries which are porous.

Was your electrode solid lead? How long did you let it sit to grow the PbO2 and what was the current density? Most of the PbO2 in the battery that I took apart had a soft fuzzy appearence. To work it probably needs to have a dense PbO2 layer that would stop penetration by Cl.

It really seams like a lead substrate would be the best choice and if that doesn't work the only way would be to somehow press loose PbO2 into sheets.

simple - 25-7-2006 at 18:18

If you aim for HOCL the best bet is DSA type anode. DSA is a brand name not the type. Same like SONY. In our salt water chlorination industry anode material is simply known as ANODE and it come in two types: reverse polarity and standard.
There are only 4-5 “good” manufactures of this type anode in the world (forget China and India)
I am not sure yet what is your aim, have to read thru forum few more times. All good anodes for sodiumhypochlorine production made using similar materials but different technics. Chlorine production can be controlled by varying power to the anode.

jpsmith123 - 25-7-2006 at 18:48

What's wrong with MMO cells made in India? They're not as good for some reason?

Don't most all manufacturers use basically the same materials and process (at least for monopolar cells)? How much variation in materials and processes could there be?

simple - 25-7-2006 at 19:28

We have tested anode materials from a lot of suppliers including India. We test to strict specs in controlled environment. Only USA, Australia, Europe can produce long lasting / high specifications anode material. None of commercial manufacturers use India material due to low quality.
Re material and process, it is like making cars! Same metal and plastics used, but you get Mercedes or KIA made.

jpsmith123 - 25-7-2006 at 22:04

As far as I know, everyone uses the dip and bake method; i.e., dipping the titanium substrate into the RuCl3 & TiCl3 solution (or whatever similar mixture they use), then baking it to oxides, and then repeating several times to get the required build-up.

IIRC, this relatively uncomplicated process has been around for at least 40 years; so unless they're doing something fundamentally and inexcusably wrong, like improperly preparing the surface, or simply not putting enough material on, etc., I can't see what part of the process they could easily cheat on that would make it worth their while.

I'm not saying I don't believe you, but I'd like to understand what could be going on here.

Anyway, do you work for a chlorinator cell OEM? And what kind of testing do you do on the anodes?

Do you know anything about the following company or their products?

http://www.vchlorin.com/cell.htm

[Edited on 26-7-2006 by jpsmith123]

Twospoons - 25-7-2006 at 22:32

Sounds like the chem industry is like the electronics industry: if you want cheap choose India/China/Taiwan... If you want quality choose EU/Japan/USA. There are always shortcuts in industry.

simple - 25-7-2006 at 22:42

http://www.vchlorin.com/cell.htm I know them, however did not test the perfomance of there's cells (electodes)

Dip method is out of date it's been outdated in mid 1980's. The coating technology is way more accurate and controlled our days. Chemical composition, you are right. Ru & Ti still used as the core elements. Hovewer technology have walked a long way since then.
Say we can produce reverse polarity anode with currect density 500Amp/meter, lifespan of 18000Hours+
This is achiwable by some other manufactures in the wold as well, but not many. As i mentioned, only 4-5 companie can do it. Technology is to difficult to duplicate. Hovewer, non reverse polarity anode can be made esier and more companies can make it.

I work for salt water chlorinator manufacturer in Asutralia. We manufacture our own anode. Took us 8 years of R&D and a lot of money. We have an acselerated life span test in plase toghether with spectrum analizers, X-ray electon microscory and so on... Some test done inhouse and some by university we subcontract.

jpsmith123 - 25-7-2006 at 23:11

I haven't seen any new patents issued (of course I may have missed them), so I assume the methods presently in use are not too different from those taught in the original patents of H. B. Beer (for the monopolar case at least).

In fact IIRC, at least one of the companies I corresponded with uses the bake on procedure, and one person told me they use an electrolytic process of some kind.

Anyway, for hobby purposes of making small amounts of ClO3 and ClO4 of course nobody here needs a bipolar cell.

What I think some here would like to get is an inexpensive replacement cell electrode set in the 10 to 20 amp range.

We don't need any plastic housing, but some threaded titanium studs or screws (and nuts and washers of course) would be required to come through the lid of the cell and accept the power supply leads.

simple - 26-7-2006 at 00:24

Nice to see someone knows Beer!
Anyway, for non reverse electrode you can get good samples from number of places.
You can get a quote from KAWANA chlorinator’s repairs: http://www.kawanachlorinatorspares.com.au/
I know this company and they supply good quality staff. Ask them about 20 -25 amp anode assembly. They will offer you a range in different configuration. You may want to get a whole set as well called “cell” it is not too much more expensive.
Just look thru there’s site it will give you an idea.

jpsmith123 - 28-7-2006 at 01:02

I'm wondering, what are your thoughts regarding mesh vs. solid plate type cell design?
IOW, with the exception of ease-of-cleaning, where solid plate electrodes would appear to have an advantage, are there any other factors which would lead you to select one type over the other?

simple - 28-7-2006 at 01:45

Mesh electrodes in salt water chlorination game been used for a long time.
From our point of view the only advantage of mesh over plate is:
1. Calcium build up on electrode doe’s not fall off easy (when in operation)
2. As titanium prices are getting high expended mesh is cheaper to use as contains less titanium but same surface area as plate (at simular size plate)
3. Suitable for use in any electrode configurations as will flow water in any direction

On the other hand plate is:
1.Can withstand higher mechanical load (vibration in water flow and abuse during cleaning process)
2.A lot better anode coating due to much more accurate manufacturing process. Mesh anode still made with rough technic (due to some processing problems) when plate anode made very accurately
3.Can pass a lot more current with minimal loss due to material crossection area

Those are few of most accepted con’s and pro’s. There are number of others which taking in to the consideration depending on the design of electrode you want to make.
Just my 2cents….

jpsmith123 - 30-7-2006 at 21:26

Thanks for your input, simple. Can I ask, have you heard of a company in Australia called "eSplash" www.esplash.com.au?

If so, I'm wondering what do you think of them and what kind of MMO coating do they use on their generic monopolar anodes (e.g., is it RuO3 or IrO2 or Ir2O3 based)?

simple - 30-7-2006 at 22:54

jpsmith123 , eSplash do not manufacture - they resell. They sourse from different suppliers.
Therefore depending on the model of the electrode different material will be used as made by different companies
As some cells are made for Reverse Polarity machines obviosly there is no Ir used.

jpsmith123 you seem to have a sugnificant knolege in electrochemistry. What do you do for living?

Rosco Bodine - 20-8-2006 at 10:54

@MadHatter

Those welding carbons are a sort of a partially graphited porous carbon material , I think , IIRC they are perhaps a blend of something like a ceramic cement , maybe an oxychloride cement with bone? charcoal which has been pressed into sticks and then high fired until it has a partially fused almost ceramic composite graphite/charcoal composition not nearly as dense as say
solid graphite like used for motor brushes .

Have you ever tried the more dense and non-porous
solid graphite material to see if it holds up any better than the porous type material ?

Also I have wondered about a coaxial electrode arrangement where the carbon or graphite anode is
placed inside a length of stainless steel pipe , perhaps
held centered in the pipe with spacers or nylon screws
on a 120 degree pattern through the stainless pipe
around the periphery near each end .

It would seeem that such an electrode placed vertically
or tilted a bit , would perhaps act as its own liquid pump
pulling fresh electrolyte across itself from any rising escaping bubbles on its inside surfaces .....along the same lines as the entrainment flow works for an aquarium filter .

Twospoons - 20-8-2006 at 15:29

If you want a self pumping electrode assembly try to imagine this: Co-axial electrodes supported by a helical spacer, which forms an archimedes screw sort of thing. Now wrap a solenoid winding around the whole thing - could even use the electrolysis current to power the solenoid. What you get is a radial current flowing in an axial magnetic field - resulting in a tangential force on the electrolyte. The helical spacer makes the resulting swirling electrolyte "screw" its way throught the whole assembly - assuming an inlet at one endof the helix and an outlet at the other. Voila! self pumping electrolysis!

It occurs to me that the solenoid could also be conveniently replaced with loudspeaker magnets, which have a lovely hole through the middle, and are magnetised axially.

Rosco Bodine - 20-8-2006 at 16:00

How about just using a stainless steel tubing coil for the cathode , and then possibly you would get the field
as if it were windings , and you could also put cooling water through it .

not_important - 20-8-2006 at 19:45

To echo Rosco Bodine :

Bubbles alone will give you self-pumping. Even with a non-enclosed electrode there will be some upwards flow of fluid, put a tube around it and the pumping action is enhanced. Consider how many under-gravel filters in aquariums work, the do a web search for "air lift" or airlift pumps. No messing around with rotating parts, which can be annoyingly difficult to keeep functional in a corrosive environment.

Twospoons - 20-8-2006 at 21:27

not_important, you mis-understand. There are no moving parts. Its a bit like this :MHD drive

not_important - 20-8-2006 at 21:53

Quote:

Originally posted by Twospoons
not_important, you mis-understand. There are no moving parts. Its a bit like this :MHD drive

You are correct, I did - haven't really woken up. However I think that MHD is hardly going to give a compact, simple pump. I think that either the intrinsic gas release, or blowing air or N2 through the tube, will work as well with a lot less fuss. The only place MHD seems to be used for pumping is with liquid metals or on a micro scale.

It's be a fun project, but I'd not mess with it if I wanted to actually use the cell for production.

Twospoons - 21-8-2006 at 14:39

It actually works better than you'd expect. I tried a very crude setup with a ferrite magnet under a dish of saline, put two electrodes in, and ran a couple of amps through. With no attempt at optimising, the saline swirled nicely around the electrodes.

YT2095 - 17-11-2006 at 04:41

just a quick (possibly helpfull) tip.

for those using Gouging rods, after you peel off the copper plate/foil, soak the electrodes in dillute nitric acid (2%) for several hours before using them, it gets rid of any remaining copper metal in the pores (and there is some!).
then wash them off in plain water and leave them somewhere warm and dry, I put mine on the radiator.

it`s just one LESS source of possible contamination

dann2 - 14-4-2007 at 16:54

Quote:

Originally posted by jpsmith123
For a cell body, I used a 1 L pyrex graduated cylinder, and for a lid, I used a slightly modified plastic lid from a jar of Skippy peanut butter, which held the electrode assembly.

The disadvantage of the "Salchlor" anode is the length; at 12 inches long, it is hard to find suitable containers that can accomodate the whole electrode. In retrospect, I think it would have been better to go with the "Autochlor" AC-20 or AC-25 chlorinator cell assembly.

Anyway, I filled the cell with saturated NaCl solution and ran about 15 amps through it, but it made more chlorine gas than I was expecting, and I was afraid it would bother the neighbors, so I shut it down

Hello,

Reading this post I was surprised to learn that someone had make Perchlorate using a pool chlorination anode. (MMO) . Then perhaps the anode was platinum or PGM based.
Anyone here know?

Cheers,

Dann2

jpsmith123 - 15-4-2007 at 18:21

Hello Dann2,

Several people have reported using pool chlorinator anodes to make ClO4. These anodes have MMO coatings, usually RuO2 + TiO2, and sometimes RuO2 + IrO2 + TiO2, which may be more robust. Apparently PdO2 + TiO2 works well also...in fact it may have better catalytic activity than the other PGM oxides, but I think it is somewhat more expensive than RuO2 and thus not generally used in pool chlorinators, IIRC.

BTW, I think I remember reading in one of Beer's patents where he claims to have successfully used graphite as a substrate for his MMO coatings.

I recently built a new cell based on a 20 amp "autochlor" chlorinator, but I have not been using it because right now I live in a very small place in a lousy area not at all conducive to experimentation.

Regards,
jpsmith123

dann2 - 29-4-2008 at 15:42

Hello,
Some info.
Reasons for the DSA Passivation during Chlorate Electrolysis and the Means for Extending the Anode Service Life.pdf

Dann2

Attachment: Reasons for the DSA Passivation during Chlorate Electrolysis and the Means for Extending the Anode Service Life.pdf (56kB)
This file has been downloaded 1860 times

dann2 - 2-10-2008 at 04:21

Some info. on Sodium Chlorate making here:

Encyclopedia of Chemical Processing and Design.
John J. Mc Ketta

http://books.google.ie/books?id=_R00NqWST6MC&pg=PA233&am...
There is some info. on DSA anodes. It says that Barium will poison them.

Missing pages here:

http://ifile.it/6gy0ish

Have a good bedtime read!!!

Dann2

[Edited on 2-10-2008 by dann2]

dann2 - 3-10-2008 at 11:52

O Deary me,

You live and learn :-|

I have just realized that Google books switch around the 'missing pages' on there books, therefor the 'missing pages' that are at the ifile.it link are no longer missing but a different set are

#~~@f%$~#~#.. *7*&+## !!!!

Is there an easy way to download books from Google books (bits of books). You can go back a week later and download the missing (on day one) pages.
You could always use the PrtSc button but it is a bit of a pain, cheap though.

Dann2

dann2 - 14-10-2008 at 13:24

Hello,

Obtained "The effect of pH on graphite wear in a chlorate cell process", thanks to folks in Wanted refs and translations in the refs. section. It gives the lowdown on Graphite erosion in Chlorate cells operated at very high pH. Up at 9 - 10 where non-pH controlled cells operate (never came accross this info. before).
It also states that Graphite from the anode is mainly lost as sludge (read: black mess) when cell is operated at high pH, as opposed to converting to CO2 when cell is operated at around neutral (as per industry).
pH control looks attractive (greater CE, less erosion per amper hour and per KG Chlorate, less actual eroded C appears as sludge) especially since it would appear that *control* as such is not really needed. Just adding HCl at a predetermined rate and checking pH twice per day (or once) will give a tight enough pH range.

The figures from Industry for Graphite erosion in Chlorate cells have always been very impressive. A graph from the article is below.

Dann2

erosion.jpg - 21kB

Xenoid - 14-10-2008 at 14:53

@ Dann2

That's an amazing graph, it explains so much!
If I remember correctly, my chlorate cells were operating in the 9 - 10 pH range

Has anyone tried the "cheap" aquarium pH controllers like the WEIPRO PH2010 ?

http://www.deepblueaquarium.co.nz/index.htm

(Check in the controllers and monitors section - the direct link doesn't work for some reason)

I gather they can be obtained for less than US$100.

dann2 - 14-10-2008 at 15:53

Hello Xenoid,

Long time no see!

I would think that the pH probe in the aquarium controllers may not stand up to the (rather more) harsh environment in the Chlorate cell.
Look what it can do to most plastics etc, what would it do to your Guppy I ask???

Also in the article mentioned above, it gives some stuff for treating Carbon with (we usually use Linseed oil).
Industrial Graphite for Chlorate cells must be porous.

Quote:
__________________________________

It might also be added that the impregnation
method described elsewhere [3] has been
developed still further, and the improvements
obtained with diacyl peroxides, and, particularly,
with dilauroyl peroxide [3], were advanced with
the use of pinan hydroperoxide [43]. The latter
is stable to higher temperatures thereby providing
the benefits described elsewhere [3], that result
from keeping the anode potential close to the
value for plain graphite and from increasing
the life-times of electrodes in a chlorate cell
process.
___________________________________

http://www.arkema-inc.com/index.cfm?pag=69
At least it's not toxic!

pinan hydroperoxide
diacyl peroxides
dilauroyl peroxide

Don't suppose they are available in hardware store etc.

Dann2

Xenoid - 14-10-2008 at 16:22

@ Dann2

Yeah, Hi! Lost interest, I've got so much chlorate and perchlorate I don't know what to do with it!

I assume the pH probe is glass with a protective plastic surround, like with the common hand held probes. It may be possible to remove the plastic and just use the "naked" glass probe. I'm not sure of the pH range of these controllers, but 6-7 pH should be no problem.

Edit:
Actually, something I tried a few months ago was a new way to vacuum impregnate a carbon gouging rod. The idea was to leave the impervious copper coating in place and use the rod like a "drinking straw" to "suck up" the impregnating medium. I did this by connecting one end of the rod via PVC tube to a vacuum pump and dipped the other end in the solution. I tried my linseed oil / siloxane mixture and also epoxy resin diluted about 50:50 with epoxy thinners. The latter mixture sets to a hard rubbery consistancy after a few days.
Unfortunately I couldn't get anything to "suck up", it may have been due to my pathetic vacuum pump (fridge compressor) or maybe it just doesn't work. Someone with a good vacuum pump might like to give this procedure a try. The diluted epoxy is quite fluid, and I would have thought it would have worked quite well. When the epoxy has hardened the copper coating can be peeled off to reveal the epoxy reinforced and sealed gouging rod.
Smoking hot melted candle wax was another possibility but it would require the rod to be kept hot to stop the wax hardening as it was "sucked up" the rod.

[Edited on 14-10-2008 by Xenoid]

tentacles - 15-10-2008 at 16:06

I recently picked up one of those very weipro type controllers. You can set the pH control between 3 and 10, I believe. They seem to work all right, but I haven't setup a new cell yet. The probes are a typical acrylic looking casing around a standard glass probe. I bought an extra probe. If the probes themselves don't survive, I'll look into a different type that would be more suitable.

Got some stuff together to make a 5 gallon bucket cell, once I get that MMO anode to play with. Going to use a solenoid and gravity to dose the cell with HCl (probably just muriatic acid) with a yoke or something to restrict flow. Tubing will be PTFE.

Also recently picked up a 5.5v 200A CC/CV power supply, and a 6V 90A CC/CV power supply.

When the MMO anodes get here, I will attempt to plate the MMO coating with LD, I'll let you guys know how that goes.

[Edited on 15-10-2008 by tentacles]

The exact model of controller : http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=230289...

The company, gainexpress.biz, lists on their website an industrial pH controller with ATC and a PC interface.

[Edited on 15-10-2008 by tentacles]

MMO Chlorinator Cell Electrodes

Xenoid - 19-10-2008 at 17:10

Here's my latest haul from the local Swimming Pool - Spa maintenance centre. Followers of the various anode threads may remember my first MMO chlorinator electrode assembly which I described in the "Cobalt Oxide Anodes" thread about December, 2007:

http://www.sciencemadness.org/talk/viewthread.php?tid=9572&a...

At the time I left my name and telephone number with the company, so they could contact me if they got any more. Well, they lost my contact details, but put the used electrodes to one side for me. Well I finally called in again today to see if they had anything, and the attached image shows what I picked up.

The 5 assemblies in the top row appear to be from the same manufacturer and have 5, 7 and 10 electrodes. The 10 electrode assembly in the top right location seems to be in very good condition. The small assembly in the lower right location has 5 solid titanium plates, but seems to have lost its MMO coating.

The electrodes were free, but I very generously gave the guys a $5 donation for their tea fund and trouble.

They said they would probably have a few more over the coming months. I also called in at another place and they also said they they would put some aside for me, although this company has promised this in the past and I have yet to see anything from them!

Like "tentacles", I have been thinking for some time of having a go at PbO2 coating an MMO electrode.

EDIT: Upon further inspection it appears that the 5 green assemblies are POOLRITE brand - each top contains 2xM5 and 1xM2.5 titanium bolts - yes, Ti bolts, they have Ti stamped on the heads. I have never seen Ti bolts before, I wondered why they were not corroded. Externally they are fitted with heavy brass nuts. There is also a large "O" ring with each top.

[Edited on 19-10-2008 by Xenoid]

Chlorinators.jpg - 54kB

dann2 - 20-10-2008 at 14:19

Xenoid: You are definitely a man of immense charm and graces (or was it the five shade clad 'heavys' :cool:

(minus the smiles) that came with you to the company premises) for managing to secure that huge haul.
The scene looks more like a photo from DeNora's repair shop that some garage Chlorate maker.
I must try some similar companys around here but swimming pools (wanted swimming pools that is) are a bit thin on the ground.

Cheers,
Dann2

Xenoid - 21-10-2008 at 14:28

Quote:

Originally posted by dann2
The scene looks more like a photo from DeNora's repair shop that some garage Chlorate maker.

LOL - Good one, Dann2

Here's a detailed image of one of the POOLRITE 5 electrode units. These are polarised in that they have 3 plain Ti cathodes and 2 MMO coated anodes. The 10 electrode assembly (mentioned above) is non-polarised and has 10 MMO electrodes. The non-polarised units have the + and - connections alternated by the controller to prevent build-up of "crud" on the cathodes. The anode assembly has a date code and is 14-12-01. The other units range in age from 1997 to 2004.

The mesh electrodes are 20cm x 5cm, and are spot welded to Ti straps which in turn are spot welded to the Ti bolts. Near the head of the bolts you can see a small grey plastic fitting with an "O" ring seal. This small "O" ring assembly fits into a counter-bored insert on the inside of the green lid. This is a great design, and it makes it very easy to dismantle (versus the epoxy encapsulation method) and modify for home chlorate use. All that is needed is a new 12-15mm thick PVC lid to suit your cell, counter-bored for the Ti bolt/"O" rings. With a little silicone grease this will provide a perfect corrosion-free and gas sealed electrical connection. The Ti bolts have a smaller brass nut to hold them in place and the larger brass nut to provide good electrical contact to the Ti bolt threads.

The small hole to the left side of the lid is for an earth or sensing electrode and was fitted with a small Ti bolt with a 3cm length of MMO wire attached to it.

One of the POOLRITE 5 element units, (dated 2004) appears to have lost virtually all the black MMO coating from the anodes and is truly worn out (but still suitable for cathodes or recoating). The other units all have usable MMO electrodes.

ChlorinatorDetail.jpg - 38kB

dann2 - 21-10-2008 at 15:45

Quote:

Originally posted by Xenoid
One of the POOLRITE 5 element units, (dated 2004) appears to have lost virtually all the black MMO coating from the anodes and is truly worn out (but still suitable for cathodes or recoating). The other units all have usable MMO electrodes.

Careful you do not condem these elements (yet). They may still have a usable MMO coat. I have a piece of corrosion prevention wire anode (MMO on Ti with Cu core). I put it in a Perchlorate cell (cell containing Chlorate) to see if it would make Perchlorate and let it run for a long long time. The black coating wore off the wire in places but the wire STILL had an MMO coating of some sort on it as it went on gassing where the black coat was gone. It just looked like bare Ti but was not. There must have been two coatings of some sort on the wire. Perhaps your anodes are similar.
Try in a cell before assuming the MMO is gone.

Dann2

Swede - 23-10-2008 at 06:40

I like the looks of those chlorinator elements, especially the plastic spacing brackets. I assume in those devices, they are HDPE or some other castable plastic, but in a chlorate cell, something similar from PET, PVC, or PTFE would be better.

I'm wondering about the ability of those light Ti straps to carry current. A pool chlorinator doesn't draw nearly as much as we would like to put through a cell, and with my own systems, I've noticed a minimum of 1" wide or so is necessary when operating at 50+ amps, otherwise, the straps will heat to the point where they will damage the cell lid or whatever plastic system used to seal them.

If anyone is interested in reworking surplus MMO mesh material, or starting with new, I found that the MMO mesh spot welds beautifully to Ti straps, which for me was a bit counterintuitive, as Al cannot be spot welded at home, and I thought the Ti would behave like Al in this regard. You can either buy and rework a cheap Harbor Freight spot welder, or make your own, but it is definitely the way to go.

Tentacles, have you located a useable solenoid valve for the HCl pH control vat? There are varieties that simply pinch the PTFE tubing, and that might be a good way to go.

[Edited on 24-10-2008 by Swede]

Xenoid - 23-10-2008 at 14:05

Hi Swede

A quick perusal of chlorinator cell specifications, for example here;

http://www.poolstuff.com.au/shop/product_listings.php?Maingr...

indicates they are designed to run from 10 - 50 amps usually as a function of the number of plates. Most 7 plate cells appear to run around 30 - 35 amps. They seem to use a standard strap geometry and fit from 3 to 10 electrodes depending on the application (pool volume, and hence current). The 50 amp cell may use thicker straps, but I don't think so.

The Ti strap on the 5 plate unit I described above has a cross sectional area of about 10mm^2 (10mm x 1mm). This size seems standard on all the chlorinator units I have seen, even the 10 electrode, so I guess it is OK for at least 30 - 40 amps - may be 50 amps.

BTW - a quick search with Google indicates Ti bolts are fairly readily available, for example in the USA here;

http://www.unitedtitanium.com/boltInventory.html

And in the UK here;

http://www.tibolts.co.uk/

Apparently they are used quite commonly on top range mountain bikes, the UK place ships worldwide and their prices look quite reasonable. I think Ti bolts have a great place in (per)chlorate cell construction. Having to use SS bolts was a definite drawback with many of my designs as they corrode badly, especially in the headspace area.

dann2 - 23-10-2008 at 14:20

Hello Swede,

Anode looks good.
How did you weld it? Is your welder a MIG welder with Ti wire or are you using a
'spot welder' (not too sure what they are universally called). ie. A welder with two Copper electrodes that clamp onto the area to be welded and a current then passes?

Did you ever try welding Ti to Ti with the spot welder? Perhaps you are having success welding Ti to MMO coated Ti because the MMO coat makes it possible (guess).

If one was too lazy to weld a Ti strip to the MMO or (God forbid) the welds cause problems you can always simple use larger piece of MMO and take it out of the cell and connect directly to the MMO outside the cell. A waste of preious MMO real estate but might be the way to go for someone who can't/won't weld.

The pH controller that has been mentioned is definitely the way to go for pH controll, better that a simple syringe pump. Hope pH probe holds up.

It makes you wonder that if Xenoid had to try his MnO2 anode in a pH controlled cell would it have lasted much much longer than it did? It lasted a long time in a non controlled cell but if the graph above for Graphite anode erosion has any relation to MnO2 anode erosion, then the MnO2 would go from being a good anode to a bloody great anode.
Easy to make at the back of a ditch. Not as good as MMO I am sure but then nothing is as good as MMO (if you can get it).

Dann2

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