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Author: Subject: Thoughts On Anodes
MadHatter
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[*] posted on 19-2-2006 at 09:32
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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.




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[*] posted on 19-6-2006 at 20:09


jp,

Any new devolpments on using your chlorinator anode?
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[*] posted on 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).
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[*] posted on 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]




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[*] posted on 22-6-2006 at 09:28
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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.




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[*] posted on 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.
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[*] posted on 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!




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[*] posted on 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?
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[*] posted on 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.




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[*] posted on 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




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[*] posted on 28-6-2006 at 09:57
Lead plates for electrode??


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.
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[*] posted on 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




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[*] posted on 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.
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[*] posted on 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.
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[*] posted on 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?
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[*] posted on 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.
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[*] posted on 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]
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[*] posted on 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.



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[*] posted on 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.
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[*] posted on 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.
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[*] posted on 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.
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[*] posted on 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?
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[*] posted on 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….
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[*] posted on 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)?
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[*] posted on 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?
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