Sciencemadness Discussion Board

Thoughts On Anodes

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dann2 - 13-6-2009 at 17:21

Hello AF,

Sorry to hear about your troubles. You should inquire from the Ti suppliers if they will give you your money back :D

It looks as if Ti is not the mother of all Cathodes after all. Thick stuff definately stands up for a long time but you do see some corrosion in it (at least some to the stuff I have used). It would have been exposed to Fluorine if that made any difference.
Hydrogen embrittlement is probably your problem and since your Ti is so thin it effected it badly and fairly quickly.
I guess you could try SS.
I have ofter wondered would Lead make a workable Cathode? You could add some Sodium Sulpate to the solution at the end and see of there is any PPT from Lead that may be in the solution at the end of run, as Lead Sulphate is insoluble.

Dann2



hashashan - 15-6-2009 at 22:00

Quote: Originally posted by dann2  

Hello,

The pH strips sound good.
I am going to purchase a Nitrite test kit for aquarims from ebay. There are cheap enough. Hopefully they will work in a tank of poison.
I had measured the density of the Lead Nitrate solution for to decide what type of beads would be of a similar density to the solution for stirring purposes. From this link:
http://www.machinist-materials.com/comparison_table_for_plas... (divide by 0.036126 to convert lbs/inch^3 to g/cc)
the best one is PEEK with a density of 1.3g/cc. Peek in not available but Perspex is available as Acrylic beads on ebay at a density of 1.218g/cc which will hopefully sink and 'mix' when stirring starts. They will add some nice colour to the plating tank if nothing else. PVC is 1.46g/cc which may do too.
Anyone any other suggestions as to what could be used? The density of Lead Nitrate solution with 350g Lead Nitrate per liter is 1.28 grams per cc.
@Hashashan (if your are still reading!!). What did you use?

Dann2


A bit late with the answer :)
I used just ceramic debris ... I took a ceramic plate and shattered it to pieces of different size( I mean really different .. starting from 2mm diameter and ending with fine dust)
It did the work

Gamal - 17-6-2009 at 12:44

About the beads.

I haven't been using a magnetic stirrer before, but my though is to cut them open, put some lead sheet in and glue them together again. Maybe u could cover the magnet in the bead and the lead with epoxy of some kind. I don't know if it's possible, just a though. it can't be that hard to make the bead sink.

/Gamal

dann2 - 18-6-2009 at 18:47

Hello,

I have been holding my breath waiting for the answer Hashashan and I am rather blue in the face :P
I think Acrylic (Perspex or Methylmethacrylate) will do the job. They can be had on Ebay (necklace making brigade) for a few dollars for hundreds of them. Approx 2mm diameter. They are slightly less dense than the Lead Nitrate solution and stay around the plating Anode when stirring starts. This contrasts with other bead/plastic pieces I have tried that are slightly more dense that the Lead Nitrate solution where they go to the outside circumference of the plating tank when you start to stir. It's a bit like a Helium filled balloon in a car (if you ever drove a car with a Helium balloon in it). When you put the brakes on, the H balloon goes flying to the back. When you accelerate it comes to the front. Going around corners it goes the opposite way to everything else (including the air) in the interior of the car. It's a bit weird and you would think the thing is possessed.......

Dann2

uchiacon - 6-7-2009 at 21:13

Hey guys,
I was interested in making chlorate and maybe a small amount of perchlorate. I'm tasked with finding a suitable anode for both of these tasks. The two options are Pt plated niobium mesh OR MMO anode.

Choices are for Pt anode
http://www.anometproducts.com//App_Themes/anometproducts/PtC... @ $5USD a square inch.
Or
MMO pool chlorinator - http://www.directpoolsupplies.com.au/prod733.htm

So I might be making a small amount of perchlorate in the futute, it'd be nice to have that option open. But is Pt still as good as MMO in a chlorate cell? Could I just get two Pt anodes and use those for perchlorate and chlorate? Will it still be pretty tough in the chlorate cell?
I'm still unsure on this, can somebody just point me in the right direction? I can only get on type of anode.

Cheers

Swede - 18-7-2009 at 15:14

MMO cannot make perchlorate, so if you can only have one anode (??) it'd have to be platinum, unless you want to attempt a lead dioxide anode.

MMO is becoming more and more common as a surplus item. A lot of the guys here bought some excellent MMO over Ti for the equivalent of $5 for a decent sized anode. Pt ALWAYS erodes, slowly, but it happens, so any platinum I have is reserved for perchlorate production.

Yes Pt is as good as MMO at making chlorate. Far more important in terms of efficiency is control of your cell parameters like temperature, pH, stirring, etc.

Look around a bit, you'll find the MMO. Good luck.

What about titanium nitride?

jpsmith123 - 21-7-2009 at 15:50

I just got a sales flyer from "Harbor Freight", and among other things the front page features some TiN coated step drill bits...so that made me wonder: Has anyone here ever tried TiN coated anything as an anode?

TiN is a hard, chemically stable, highly electrically conductive ceramic material that's commonly found as a coating on drill bits, end mills, etc.

Of course high speed steel likely isn't a good substrate, but from what I've read, it seems it may not be too hard to make sintered TiN pieces or to coat a piece of titanium with it.

I'm going to look and see if I have any expendable old TiN coated bits here somewhere and if not, I may stop by Harbor Freight and see what I can get cheap, just for a quick experiment.


12AX7 - 21-7-2009 at 15:53

One absurd way to make TiN is burn titanium in air. I've done this before, point a carbon arc torch at a hunk of titanium, it melts, boils and combusts, leaving a brittle, spongy mess that used to be metal, and a haze of deposited yellow smoke around: nitride. I didn't check if it was conductive...

Quality TiN is probably made by CVD... not really an accessible method unfortunately.

Tim

jpsmith123 - 21-7-2009 at 16:30

What about taking a piece of Ti rod and heating it (a job for your induction heater) in a pure nitrogen atmosphere? Also, I read where sintered TiN pieces are made from powdered Ti burnt in a pure nitrogen atmosphere.

12AX7 - 21-7-2009 at 23:36

Last time I was heating titanium, it was yellow hot, in air, stable.

Personally I'd rather blast the fuck out of it with an arc welder. :D

Tim

jpsmith123 - 22-7-2009 at 08:17

Well I think we're getting ahead of ourselves a little bit. Maybe TiN is completely useless as an anode coating. Being that TiN coated tool bits are relatively common and inexpensive (at places like Harbor Freight at least), I thought maybe a quick test in NaCl solution would be in order.

hashashan - 22-7-2009 at 13:33

Damn, im actually working on Ti coated with TiN at these moments :)
I still claim the idea as mine because i started to work on it about a month ago :P however the setup in my lab broke and it is being fixed.
I hope that next week ill have my first baby running.
tools with TiN wont work because the smallest hole in the coating will degrade the whole anode.
you need to have either a perfect coating or a valve metal coated with TiN or TiC. (ZrN and ZrC are also accepted).

Im making my anodes using PVD. Vacuum arc deposition in very diluted nitrogen atmosphere(about 2 Torr)
so just wait and ill tell you about any progress

12AX I dont think that ull get proper TiN that way. I believe that it wont be as conductive and as protective as pure TiN. Im not sure how it is even possible to get direct Ti+N reaction in such a low temperature. an arc enchanced process would be plausible, but once again do it under nitrogen and not air. the TiO2 will absolutely ruin everything.

sintering at home????? i really dont think ull get anyhting close to workable that way.
and about getting ahead of ourselves ur not right. maybe the coating wont be perfect for an anode.
but I do believe that it will be really good as Ti->TiN->PbO2 buffer. if it is thin enough it will do great.
[Edited on 22-7-2009 by hashashan]

[Edited on 22-7-2009 by hashashan]

jpsmith123 - 22-7-2009 at 21:15

Quote:
Quote: Originally posted by hashashan  
Damn, im actually working on Ti coated with TiN at these moments :)
I still claim the idea as mine because i started to work on it about a month ago :P however the setup in my lab broke and it is being fixed.
I hope that next week ill have my first baby running.
tools with TiN wont work because the smallest hole in the coating will degrade the whole anode.


Of course I didn't mean to imply that TiN coated tool bits would suffice for a practical anode; my suggestion was to use what's readily available as a quick test to merely get an idea if further effort is warranted. That's all.

Did you read the "secret" research paper on the search for perchlorate anode materials to replace Pt and PbO2 (posted by Dann2)? In case you didn't, that's what the authors did; i.e., they did quick tests with variously oxidized surfaces of pieces of tool steel, IIRC.

In any case, being that you claim to be investing some real effort into this, I assume you've already done some kind of test or have some favorable information? Or you're doing the whole thing on a hunch?

Quote:

you need to have either a perfect coating or a valve metal coated with TiN or TiC. (ZrN and ZrC are also accepted).


Well of course.

Quote:

Im making my anodes using PVD. Vacuum arc deposition in very diluted nitrogen atmosphere(about 2 Torr)
so just wait and ill tell you about any progress


Why not just heat a Ti rod with an induction heater in a pure nitrogen atmosphere? Why wouldn't a layer of TiN form in nitrogen just like a layer of TiO2 forms when O2 is available?

Quote:

12AX I dont think that ull get proper TiN that way. I believe that it wont be as conductive and as protective as pure TiN. Im not sure how it is even possible to get direct Ti+N reaction in such a low temperature. an arc enchanced process would be plausible, but once again do it under nitrogen and not air. the TiO2 will absolutely ruin everything.

sintering at home????? i really dont think ull get anyhting close to workable that way.


According to Wikipedia:

"Bulk ceramic objects can be fabricated by packing powdered metallic titanium into the desired shape, compressing it to the proper density, then igniting it in an atmosphere of pure nitrogen. The heat released by the chemical reaction between the metal and gas is sufficient to sinter the nitride reaction product into a hard, finished item. See powder metallurgy."

I realize nothing's ever easy, but it doesn't sound too awful daunting for some of the resourceful people on this forum. In fact, hasn't Dann2 done some sintering?

Quote:

and about getting ahead of ourselves ur not right. maybe the coating wont be perfect for an anode.
but I do believe that it will be really good as Ti->TiN->PbO2 buffer. if it is thin enough it will do great.


Well I'd like to see if a TiN coated tool bit will hold up for a little while in a cell without sliming off in an hour like the cobalt oxide did.

hashashan - 23-7-2009 at 01:18

Im doint it by means of VAD just because I can. Im doing my thesis in a thin coatings lab and one of the students is doing his thesis on TiN coatings using VAD :) so all i need to do is to put my sample in the chamber. Thats why im not really investing too much effort in this. The information i got is just the one you got. TiN is a conductive material and it withstands some severe coroding conditions, thats it.

why not using just induction heating ... I just think that the heat will not be sufficient. It will be much more effective to do the heating with an arc because it will ionize the nitrogen and the reaction will flow much better.

about sintering .. i think that compressing will be the main problem, I believe that the pressure that is required will be much too high.

JohnWW - 23-7-2009 at 06:21

TiN, although very hard and used to coat drill bits etc. as the result, is also very brittle, which poses a major problem in the fabrication of articles made from solid Ti, such as the hulls of supersonic fighter jets/bombers able to withstand higher temperatures than Al alloys, as well as anodes. Casting and welding of Ti articles thus has to be done under argon.

Swede - 23-7-2009 at 11:48

Notes on laserred's "eBay" MMO mesh

Quite a few guys purchased mmo sheet from a guy on eBay. The material is about 3" wide, with a 90 degree bend at one end. This material is very effective, and produces chlorate as efficiently as my large commercial sheet. But...

A goodly portion of the MMO is coated with a red/brown smut. What this material is, I have no idea. It doesn't seem to harm the process, and appears benign. My guess has always been that these MMO sheets were clamped into some sort of cell for a chlor-alkali process, perhaps even a chlorine generator? I don't know.

The differences between it, and the commercial sheet, beyond the smut, is that the coating needs to be scraped off where any spot welds are placed. Further, if you apply an ohmmeter along 6 inches or so of the sheet, with the probes on the coating, the resistance is fairly high.

I don't know why I decided to try this, but I took a scrap, and soaked it in 32% HCl for about 3 hours. The brown smut was completely removed; the HCl took on a bright yellow tint. When I measured the resistance, it was 1/10th of the value along a similar, unsoaked piece. It is still higher than the commercial sheet, but the removed smut was definitely inhibiting electron flow a bit.

With a decent lab, I could figure out what the yellow tint is from. I don't think it is ruthenium oxides in HCl. As far as I can tell, little to no actual MMO was stripped, just the brown stuff. So if you feel the need to clean this material, 32% HCl works. I wouldn't go longer than 30 minutes... I don't think there is a need to, as the yellow appeared within 1 minute, and did not get appreciably darker. Even more interesting, I tried Caro's acid on a piece a while back, and even that didn't touch the smut, but plain old HCl does.

Do you need to clean it? No, I don't think so. It may allow welding without scraping spots, but overall I don't think it's necessary.

Swede - 23-7-2009 at 12:39

^^^ Follow up:

Thinking that the cleaned eBay MMO might spot weld adequately to commercially pure titanium without scraping the coating from the junction areas, I tried a spot weld without scraping.

It appeared to work, but a modest tug on the single spot broke the joint. The same piece, same weld, when properly scraped, is about 5X as strong, so scraping still appears to be necessary.

The easiest way to clean the spots in preparation for welding is with a dremel tool and a fine sanding drum. A few gentle passes of the drum over the triangular areas (where the weld takes place) works quickly. A dust mask is a good idea - you don't want to be breathing ruthenium oxide dust.

One last note on adapting MMO sheet in general to Ti straps - creating a leakproof, easy to use fit between the rectangular strap and your cell is a pain. Today, in another experiment, I took a section of CP titanium tube, slotted it, and attempted to crush it over some MMO mesh to flatten it in preparation for welding. This worked poorly... the Ti cracked and it was a mess.

A simpler method was to heat the plain tube end dull red, and flatten it thorought in an arbor or hydraulic press between two good pieces of steel. It came out very flat and even. This flattened portion was degreased and welded to a section of MMO mesh. I now have a cylindrical strap, which is infinitely easier to use. All you have to do is take an appropriately-sized compression fitting, preferably of PVDF plastic, and if your tube is 1/2" OD, drill the compression fitting entirely through 1/2". The tube is installed from the bottom, the ferrule and nut added, and it's tightened down. You now have a leakproof, threaded fitting that can be adapted to your cell.

Down with salt creep and chlorine gas! :D

Bikemaster - 24-7-2009 at 09:15

I buy 3 of those "electrode" and i was suspicious too about the red/brown color. I d'ont even test the electrode but i buy it to make lead dioxide anode ... so i was d'ont really care about the quality of the mmo coating.
Your theorie seem to be plausible, maybe they are old anode... that may explaine the low price of the mesh.

Swede - 25-7-2009 at 05:52

The brown smut does not seem to harm anything when they are used for chlorate, but in the future, if I attempt further LD coatings on this material, I will absolutely pickle it for a decent time period in HCl prior toplating.

hashashan - 28-7-2009 at 07:54

Yey, the samples are ready. I hope that Ill start the experiment today or tomorrow.
However a professor from my lab told me some bad news, he said tht he recalls that TiN pits while doing electrolisys in the presence of ClO3 ions so im not too optimistic.
anyway im going to dry this.

These are the two anodes. one is Ti foil coated with TiN and the other one is a Ti rod with TiN coating. the coating is very thin, sub micron.



[Edited on 28-7-2009 by hashashan]

jpsmith123 - 28-7-2009 at 09:07

Well, nothing ventured, nothing gained I suppose.

Can the professor point you to any literature on the subject?

I haven't been able to find much at all on it. The only relevant thing I could find was a 35 yr old patent (US#3788968) which suggests usint TiN as an intermediate layer on an anode.

hashashan - 28-7-2009 at 10:13

He told me that he once did an experiment like this on his own, however he is quite sure he did it with HClO3, and HClO3 is much more agressive then a NaClO3 solution.
an an intermediate layer, well yes; if it wont work as an anode it will be a perfect intermediate layer, much better then the MMO, for me it is easier to get TiN then MnOx or SbOy/SnOx

hashashan - 29-7-2009 at 00:30

Well, I have some bad news. I fired up an electrolysis yesterday and I got very weired results. The Ti-TiN works like a diode, it does not conduct as an anode.
As a cathode the coating peels off :(

I guess that the only chance is an intermediate layer. Now well have to wait until Ill make a PbO2 coating.

jpsmith123 - 29-7-2009 at 09:48

Sorry to hear about your discouraging results.

I just borrowed a TiN coated drill bit from a neighbor and electrolyzed brine with it for about 30 seconds (I didn't want to risk ruining it on him) in a stainless steel cup, and it seemed to work fine; i.e., a few volts gave a constant few hundred mA.

Then I took the bit out and looked at it and I couldn't see any obvious signs of damage...of course 30 seconds isn't long enough to say anything about it except that it seems to have good conduction.

hashashan - 29-7-2009 at 16:13

very weired,
I had a chat with the professor again and he confirmed my results .. he said that it doesnt conduct as an anode and gets destroyed as cathode(not what he said last time but he is a weired dude)
anyway few volts over hundreds of mA is what I call not conducting :) 5V in a small cell should easily give you several amperes.
I did get some bubbling when using TiN as anode but it was extremely unefficient.
well I guess Ill have to do more experiments, maybe in a more controlled environement,
jpsmith are you sure you used it as an anode and not cathode?

Swede - 31-7-2009 at 06:33

New Spot Welder rig

I've tried both TIG welding and spot welding to create anodes and cathodes of CP Ti and MMO in various sizes, and it turned out spot welding was infinitely easier and more effective than TIG, unless you have a very high-end TIG machine that can create a stable arc of just a couple of amps. Anyway, my old spot welder had been made from a rewound transformer, coupled to a pair of clamp arms and a timer + foot pedal.

I was making up a bunch of MMO + Ti anodes, and my old homemade welder just wasn't hacking it... not enough current. I decided to try Harbor Freight's 115V spot welder. Not the cheapest, but the results are spectacular compared to my homemade welder.

I took the harbor freight welder and modified it extensively. As it came out of the box, it was a handheld clunker with a simple ON-OFF switch under the handle. I pulled the switch, found it was simply 115V for the primary of the transformer, and routed them instead to a timer-controlled solid state relay of 40 amps.

The handle was modified, and the welder itself clamped to the same aluminum plate used earlier.



This setup is AWESOME. If $$ is not a big object, and you want to do a bit of spot welding for technochemistry, this is a decent way to go. A 1/2 second weld time easily welds MMO mesh to Ti sheet of 1.3mm thickness, and I have no doubt it'd do several mm if needed.

The timer (red thing) is a "National Controls Corporation" model TMM-0999M-461, set to "1-shot" function on the control face.

Here is a basic diagram for this timer when coupled to a home-modified transformer. To adapt the HF welder, the 2 wires in the handle are simply attached to the SS relay output side.






dann2 - 1-8-2009 at 11:57

Hello,

Nice job Swede, as always. I have a 180 amp (stick) welder and I must rig up some sort of a spot welding attachement some time. What metals can you make the actual 'pincure tips' from. Does it have to be Copper. Wonder would very thick steel? do or perhaps use steel bars with Copper pieces on the ends where the welding actually takes place. I have no long large Copper bars but would have two short bars.

Some stuff here
http://pubs.acs.org/doi/abs/10.1021/es970578h
about attacking marine bacteria with TiN electrode. The highest Voltage used was 0.8 Volts (afaics) versus AgCl (how much 'applied' Voltage, as we would say, that related to I don't know but it is low as they say it avoides the release of Chlorine. Is this to save the electrode?


On a different note there are two papers in the reference section in "Wanted References and Needed Translations (5)" regarding Barium Chlorate and Perchlorate making that may interest some here. Posts are dated 31 July 2009.

Dann2

[Edited on 1-8-2009 by dann2]

watson.fawkes - 2-8-2009 at 12:03

Quote: Originally posted by dann2  
What metals can you make the actual 'pincure tips' from. Does it have to be Copper. Wonder would very thick steel? do or perhaps use steel bars with Copper pieces on the ends where the welding actually takes place.
The magic keyword for searching is "resistance welding". The AWS has a handbook on the subject.

The heuristic to think about this is that each thickness of metal is a resistor and also each metal-to-metal junction is also a resistor. Heat develops in the areas of high resistance. That means heating steel with a steel tip is sure to weld the tip to the work. You use low resistance tips (copper) in order that the resistance heat be generated in the work piece.

Paradoxically, you use tungsten tip buttons to spot weld copper. Here the heat is generated in the tip and transferred to the work. The weld bead is a different shape. This technique works because the melting point of copper is lower than that of tungsten, and so you tend to melt the work rather than the tip.

You can use steel to hold the tips up mechanically, but if you do, it's best to use a separate current conductor to avoid long cooling-off cycles.

Swede - 3-8-2009 at 06:52

WF is correct. I've tried Copper, tungsten, and brass. The latter two did not work well. The brass did work, but left behind touches of zinc slag, and the tips tended to stick to the work.

Copper bar can be a pain to work with, let alone find. It usually has to be ordered. For this sort of work, the tips also need to have a cross section of maybe 1/8" or 3mm, and an included angle of 90 to 120 degrees.

Solid Ag would probably work very well! :D Whatever is used, the resistance needs to be as low as possible, or they will heat ferociously.

Edit: I also noted the AC voltage of the arms on this rig are 1.6 volts vs. 4 volts for my homemade job. In the transformer, fewer secondary winds = lower voltage = greater current. On my homemade rig, if I had taken a couple of the secondary winds off, I might have been able to jack the current up a bit, but the secondary, of #4 stranded copper, was already heating up too much. It couldn't have carried more current. The transformer was just too small.

Hacking the HF spot welder is not the cheapest way to go, but it does work very well indeed and will save a lot of time.

[Edited on 3-8-2009 by Swede]

Swede - 6-8-2009 at 07:28

Testing for nitrites in a Lead Dioxide plating bath:

One of the problems seen by many is that the useful life of a lead nitrate/HNO3 bath to plate LD appears to be limited. Even when the lead is replenished, for some reason, plating quality deteriorates. This is bad, obviously - a few liters of Lead Nitrate solution is both a hazard and expensive.

One proposed contaminant was nitirites. I picked up a test kit for nitrites (aquarium) that appears reasonably sensitive... first test was for interference from nitrates. A solution of KNO3 in distilled water showed zero nitirite. Next, a sodium nitrite solution was tested with known quantities of nitrite, and the kit picked them up just fine.

I tried testing some used plating solution for nitrite with this crude kit, and it showed zero. This does NOT mean there are no nitrites... but it is encouraging. The possibility exists that the ionic species hash that is used LD plating liquor interferes or otherwise prevents the kit from detecting nitrites.

I do not know the mechanism of this particular kit. I need to do a bit of study and perhaps come up with a reliable test to see if nitrites ARE a problem when plating LD.

dann2 - 6-8-2009 at 11:08

Hello Swede,

This is good! I purchased an aquarium Nitrite test kit some time ago but did not get time to test some solutions. Still have to buy some Nitrite. It is sold as an engine anti corrosion additive for vehicles.
If you add a tiny amount of the Nitrite to a small quantity of Lead Nitrate plating solution they you can see how good the test kit is for our job. Start with a tiny amount.
There may be Nitrites in the (your actual solution that you tested) plating solution when it is been used and soon after. Nitrites get oxidized by air back to Nitrates. How long it takes I have no idea (assuming what I am saying is indeed correct). One guy suggested bubbling air through used plating solution to get rid if Nitrites. Guess the O2 of the air is going what the H2O2 does in some of the patents.
You could even try destroying the Nitrites (H2O2 or air) after you test for them (after adding the Nitrites and hopefully getting a positive test using your kit).
Currently working on a pump for pumping Lead Nitrate solution. I have a peristaltic pump that will do the job in conjunction with a timer but I am trying to set up a pump + timer that uses air going into a bent tube for to pump the (small amounts) of plating liquid.
My thinking is that the air going through the solution in the pipe will keep Nitrites at bay? It makes a very relaxing sound too!! Currently testing with an Ammonium Nitrate solution (saturated, density approx. 1.3, similar to plating solution). Its inclined to bung up sometimes. I think it's the AN solution evaporating when its gets warm (70C) and going solid somewhere. This may happen with plating solution too, so may need to use peristaltic after all.
Need to get a move on.
Dann2

Swede - 7-8-2009 at 08:18

I think movement of air through the solution would be a good way to go, at least as a start, being gentler than peroxide. I don't know if a peristaltic pump alone will provide adequate contact between the plating sol'n and atmospheric oxygen. You could always use a bubbler, but I would be very hesitant to use one outside of some sort of sealed chamber due to misting. I definitely need to get going some more.

I've continued my examination of the Laserred MMO mesh. I've got quite a bit, and overall, I am very pleased with it. There are some areas of contact where the Ti is slightly exposed, but you can easily create 6 3" X 5" MMO anodes from one sheet. I set up a jig on my bandsaw and ripped off that 90 degree "L" portion with little fuss on several sheets.

The brown smut is ever-present. Some sheets have more than others, but they all have it to some extent. I reported earlier that HCl cleans it up well. I did some more experimenting, especially with an ohmmeter. On an untreated sheet, the surface resistance can be high. I've measured it in the 20 to 30 kilohm range even on portions of the sheet with no smut. But an HCl pickle not only removes the smut, it apparently strips some other contaminant, not necessarily visible, and the pickled sheet shows near zero resistance, in contrast.

I took 6 sections of the "L" I removed, and pickled them all for various amounts of time in 16% HCl. I took a seventh piece, and pickled it for 6 hours in 32% HCl. None of the strips in the 16% HCl cleaned up nearly as well as the one in 32%, and as far as I can tell, even the 32% cannot touch the actual MMO; it simply cleans it very well.

On the left is a piece pickled for an hour in 16%... the one on the right, 6 hours in 32%.



The 32% actually only needed about 15 minutes to clean, but I left it in for a long time to verify that no actual damage will occur. The surface resistance of the 32% piece was nil, and it spot-welded instantly with no scraping needed. Conclusion - pickle away in 32% hardware store muriatic all day if you want. It definitely does a good job.

The HCl will become brilliant yellow. Use caution - I have no idea what this contaminant is, and it would be wise to treat it as possibly toxic. Handle uncleaned sheets with gloves, and dispose of the used HCl in a responsible manner.


Swede - 7-8-2009 at 16:46

dann2, I realized I didn't really address your nitrite question very well. My problem now is that my workspace is about 130 degrees F, literally. Every operation that requires a decent clear space, or is potentially hazardous, such as working with the Lead Nitrate plating bath, is on hold until the weather changes. I cannot describe how hideous it is. The best I can do is putter until my shop cools down.

If nitrite is a short-lived species that is created during the actual plating process, any serious experiments for me will have to wait a bit. The best I can do right now is see if the aquarium kit can detect added nitrite to used plating bath liquor.

Since nitrite is exceptionally poisonous to fish, the kit is designed to be fairly sensitive. The kit I bought is by "Aquarium Pharmaceuticals" and is designed to detect as low as 1/4 ppm. Interestingly, the base color (0 ppm) is an aqua color that is identical to the color of my particular plating bath, which contains nickel nitrate. In other words, even before the reagent is added to the sample, the sample starts with the same color as the "0" scale. Adding the test reagent doesn't appreciably darken the color. What I'm trying to say (badly) is that even with nickel nitrate (added as a grain refiner) I am hopeful the kit will work. But given the acidity, the strong lead nitrate presence, it will be hard to say if it will work until additional tests are done.

I need to scour the web and my own book resources a bit and see if I can find the basis behind the test kit. If we know what the test reagent is, we can determine if it will be effective. If it's not, we can possibly find one that is. I have a college text named "Quantitative Analysis". I'll see if there's anything in there on nitrite.




[Edited on 8-8-2009 by Swede]

dann2 - 11-8-2009 at 16:05

Hi Swede,
The test kit I have is exactly the same as yours!
There is a test at this link using Sulphuric acid and Ferrous Sulphate.
http://en.wikipedia.org/wiki/Nitrite_test
but I reckon it would be useless as when you add Sulphuric acid, Lead Sulphate will ppt. I think the Nitrate ion will not interfer as per reading on the next link below at where it says: 'Parameter Overview'
Hach do a Nitrite test at this link:
http://www.hach.com/hc/browse.parameter.list/PAR114/NewLinkL...

Another test kit here says:
______________________________
CHEMISTRY OF COLOR REACTIONS
Nitrite reacts with two acids in the Nitrite Powder Pillow Reagent (sulfanilic and then chromotropic) to form a red complex whose concentration is directly proportional to the amount of nitrite originally present. By measuring the intensity of the reddish complex with the color comparator, the concentration of the nitrite is easily determined.
______________________________

Perhaps that's what is in all Aquarium kits?

Another test (attached picture) from link below:
http://www.springerlink.com/content/p425v73427852116/


Test strip below:
http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&am...

You can make Sodium Nitrite using Lead Metal and Sodium Nitrate. Melt Lead and stir in Sodium Nitrate. Other product is Lead Monoxide (Litharge). Now let me see, where did I see a useful idea for using that stuff...............

If you read patent US 5558772 it says that Nitrobacker Agilis (the little bugger :D ) which in present in air converts Nitrite to Nitrate but that bacteria is hardly able to operate in a plating solution.

This post is becoming a bit of a ramble..........

Regarding the pump I was setting up to pump plating solution from one beaker into another beaker, I have given up on the air driven type. Apart from the splattering that was occuring (it could be controlled using a cover) the air pipe is inclined to plug with crystals from small amounts of solution what would make it's way into the air pipe and then dry off with the stream of air going past (and deposit the crystals). This type of pums is not suitable for pumping solutions IMO. Only simple liquids. So I am onto the Peristaltic and timer set up. A syphon returns the fluid back to the original beaker. I am using a conc. solution of Ammonium Nitrate, density about 1.3.

130F THAT'S hot.

Dann2




nitrite.JPG - 70kB

Bikemaster - 12-8-2009 at 05:51

I have a problem with my mmo anode. I bought it 10 month latter from north star pyro, and the anode is already dead...

Last time i go see my chlorate cell, it was full of rust (i use high quality stailless stell and sometime is can make black stuff, but this time it was really the orange color rust). When i pull out the electrodes from the mess, the anode has a line of gray color just at the level of water when the anode was in the cell. The gray line is 0,5 cm wide. I am pready sure that it is TiO.

Cell specs:

- 7,5 volt
- 3,25 amp
- 2L
- mmo anode
- stainlless stell cathode
- no ph control
- no temperature control

p.s.: The anode was running for 8 month in those condition. But in the last 3 month, i let the cell run up to the end ( well under the 100g/L of KCl). beffore that, i was getting the kclo3 out and refressing the cell all week.

Now, I have 2 question. First, can this anode can always be turn to a lead dioxide anode, and can i use this anode as a cathode???
I pay 80$ with shipping for this anode, it is why it should be nice to reuse it:P


thx

[Edited on 12-8-2009 by Bikemaster]

anode 666666666.bmp - 895kB

Swede - 12-8-2009 at 08:30

Your voltage seems high, and current seems low. Normally, 7.5V would create 50+ amps with a 2 cm electrode spacing, given a power supply capable of such current. High voltages can cause problems with this process, and make anode erosion more likely.

It's hard to tell from the photo... it does look like MMO has been stripped from the area directly below the welds, but the bulk of it still appears to have MMO coating.

If the silvery area is stripped of MMO, then yes you have bare titanium which creates a protective oxide under normal circumstances, and while it can't make chlorate, at least it should not disintegrate.

If the silvery color is some sort of coating OVER an underlying MMO, then perhaps it can be removed with gentle brushing (toothbrush) and/or acid pickling.

If it's gone, you've still got a significant percentage of MMO on the bottom, and it should still make chlorate. Have you tried it with fresh electrolyte?

On the cathode - I know there is some question as to hydrogen and other problems with titanium, but I am still convinced that commercially pure Titanium is the best and most cost-effective cathode for a cell. Unless it is abused, a CP Ti cathode seems to last forever. I even go to the trouble of using only commercially pure titanium, rather than the titanium alloys. CP Ti is easier to cut, weld, and work, than Ti alloys, and I think it creates a cleaner process. Yes, SS works, but every time the electricity is OFF, I think you are having measurable erosion and the cathode is probably dumping undesirable ions into the liquor. It is difficult to work with a cell with the power on all the time, and as soon as the power is off, there's no longer any cathodic protection. I know factories use SS for low cost, but they also have much more control over the process than we do.

@ dann2 - what little research I did on nitrites and their detection so far all point to the formation of a highly visible azo dye, with the color intensity corresponding to nitrite levels. It would be a hassle, but it might be possible to "clean" a sample first by precipitating the lead and perhaps neutralizing the nitric acid, with the idea being the creation of species that will not interfere with the test, while at the same time not adding to, or dropping, the nitrite level in the sample. It might be as simple as adding magnesium sulfate in excess to drop the lead, perhaps lye or a carbonate to neutralize (if needed) and decanting or pipetting the resultant liquid for a nitrite test.

dann2 - 12-8-2009 at 09:08

Hello,

What power supply are you using. Would it have failed and was putting an ac into the cell so that the SS 'cathode' will be eroded big time (it will be an anode)?

What are the dimensions of the Anode. If you know that you can tell the current density on the Anode. It is really the current density on the surface of the Anode that counts for erosion and not the Voltage accross the cell. (ignoring low Chloride levels etc)When the Voltage accross the cell is high(ish) (as your cell Voltage is) it can be simply caused by bad connections, too much spacing between Anode and Cathode or skinny wire etc. This does not really matter as it only wastes power. If the current density on the Anode is high (too high) then that will require an excessive Voltage which can be an indication of problems. (too high cd on Anode).
We dont really know how long MMO lasts in a non pH controlled cell with unknown Chloride levels + varying (too high) temperatures + high/unknown current density densitys on Anode etc etc. Perhaps 10 months in good. Perhaps that's all you can expect. Low Chloride levels absolutely eat Graphite.

If using as a Lead Dioxide Anode substrate try and find out what areas of the Anode still have MMO on them. Lower the Anode into a cell slowly and see what areas of the Anode have some gas coming from them. No gas = no current coming out of that Anode area = Ti Oxide coating (no MMO).
If most of the Anode has MMO then it should be OK as a substrate. You could always coat with Tin Oxide................

Dann2

Dann2

Bikemaster - 13-8-2009 at 07:55

Not deap enough... i think is one of my problem. because, in winter they have no really evaporation, but in summer, the water evaporate much faster and sometime, only the midle of the anode is in the water.

An other think, now, with multimeter a can really see how much amp that pass in my cell. And i don't now why but i got more that the maximum of the power supply. For exemple, my power supply is rate max 3A but i can get up to 4A (not just for the first few days). Can this be bad for my power supply or my electrode???

And yes, ss always put some inpurity. The water always turn to a light green and some blach stuff drop in the cell, but not alot.

dann2 - 13-8-2009 at 08:29


What are the dimensions of the Anode?

Have you any Copper wire connections that are causing the Green colour?

Dann2

Bikemaster - 13-8-2009 at 08:36

anode : 2x6
catode : 2x6

and yes the copper part that touch the electrode always turn green. i just sand this part between all batch.

User - 19-8-2009 at 05:03

Does anyone know any decent suppliers for MMO anodes located in europe?
The ones i found so far are so darn expensive that i might be as well of with Pt wire.

dann2 - 28-8-2009 at 04:57

Hello,

@Bikemaster
I presume it's 2 cm by 6 cm. Thats a surface area of 2 x 6 x 2 = 24cm squared assuming a flat plate.
Looking at the picture of the Anode I am going to guess that the Anode has approximately one third (it may be less) of this area = 8 cm squared.
Running the Anode at 3.25 Ampers gives a current density of 400 mA per square cm.
That's considered high for MMO. Just goes to show how tough the stuff is.
I presume you have one Cathode and it is to one side of the Anode.
You could cut you Cathode in half and put each half on either side of the Anode so that current distribution on the Anode is more even. It is hard to guess how uneven current distribution on the Anode is when the Cathode is on one side only. The Anode will be inclined to wear more on the side nearest the Cathode because of the higher CE on that side.

@ User Try Googling for Corrosion control companys, Cathodic protection companies, or of course the water chlorination people (swimming pool supplies).

............there's always Graphite with acid dripping into cell............

Dann2

What a fine day for the PMMMO this is!!! :P

block.gif - 3kB

Bikemaster - 28-8-2009 at 05:44

oups... it is 2x6 inch for the anode and the cathode.

But the idea of making 2 cathode is not bad. I will try it.

thx

[Edited on 28-8-2009 by Bikemaster]

dann2 - 28-8-2009 at 13:24

Hello,

There is definately a conspiracy going on on the board to keep the dimensions of that Anode from me!!
I attach a screen capture of you last post Bikemaster. Whatever character you put in for inches? or centimeters? has come out my end as the word 'Text' in bold (to boot!) ;)
Did you mean inches or did you actually mean to write 'Text'. If so I don't understand what you are saying.
Cheers,
Dann2


txt.GIF - 4kB

iHME - 29-8-2009 at 09:38

It clearly reads as inch in my end.

"oups... it is 2x6 inch for the anode and the cathode. "

dann2 - 29-8-2009 at 13:07


Thanks for that.
'inch' is showing up OK in both post now.

Quite an big Anode then, low current density.

Dann2

[Edited on 29-8-2009 by dann2]

dann2 - 2-9-2009 at 17:58


Hello,

Going back to the topic of making Perchlorate with a Graphite rod in a cell with a divider...
It was suggested to use a 'Lambskin' condom. I took this to be (literally) a piece of Lambs* skin around the Graphite (like a condom).
Granitstaterecovery (name of poster) was referring to a 'Lambskin' rubber (as in, how would I put it, a dick cover... LOL).
From a reputable publication, page 18, from here:
http://www.thevespiary.org/Naf1/Fester/AdvTech.pdf
I quote:


"netic stirrer. Clip a well scrubbed Kling-Tite Naturalamb rubber
in one side of the beaker, and put a piece of lead about viinch
in diameter, and a few inches long, inside the rubber. On
the opposite side of the beaker, stand up a one ounce ingot of
palladium Using alligator clips, make contact with the ingot,
and with the piece of lead. Next pour most of the dilute sulfuric"

The Author is not making Perchlorate etc btw but he mentions the divider. Will have to try it for Perk. Perhaps the cell conditions will be too harse in a Perk. cell.

Will any condom do or does it have to be a 'lambskin'. Not too well up in condom varieties. I find it hard to belived they will allow electricity through.

edit:
FFS, I Googled 'Lambskin' and it come up first with the word Condom after it, with a hits rating of 30,000.
It appears that they are made from Lambs intestines.
Brings a whole new meaning to the threat, 'I'll have your guts for garters'........
Now where can I get a dead sheep. Hope, when and if I do find one, that it does not ravish me. It's happened before you know...... ;)
Good Night

Dann2


*(an in: meaa, meaa, bleat, bleat, four legs good, two legs better. four legs good, two legs better. four legs good, two legs better, four legs good, two legs better.)

[Edited on 3-9-2009 by dann2]

barbs09 - 3-9-2009 at 14:51

I guess modern science has produced better membranes since the use of lambskin but the use of what’s at hand (lamb skin intestines??) is what we are all about. Pig intestine skins are widely used as sausage outers and may have the same characteristics.


I find it no surprise that such material conducts electricity/permits ion mobility after all didn't life evolve intestines for the diffusion of water and ions out of the poop shoot into the blood stream?

I will watch the development of this perchlorate route with interest

Enjoy catching your lamb -ask one of the ozzy members if they have any spare Velcro gloves :D (couldn't resist!!!)




Swede - 4-9-2009 at 11:02

I finally figured out a way to adapt a round Ti tube as an electrode shank, which gives one the huge advantage in a secure (yet maintainable) setup using a stock PVDF compression fitting.

In a nutshell: Flatten the tube at one end, weld to the electrode. At the other end, install a plastic plug inside the tube, then hammer in a brass or similar threaded fitting for the electrical connection.

Flat straps are a pain - here is a way to use a round shank for many electrochemical processes.

The MMO pictured is the "Laserred" material after pickling in HCl. Laserred is not currently offering any more on eBay. It was a tremendous bargain... maybe he'll be back.






Bikemaster - 4-9-2009 at 14:18

I got 3 of those mmo from lassered... it was a real good deal.

swede, i got some question for you. Can i use a simple grider to cut the piece in pieces??? and can i use a simple welder to weld the handle (with a rod for weld titanium).

and those cut and welding will let some titanum expose. Will it make proble to the anode.

thx

Swede - 4-9-2009 at 15:14

Exposed Ti is not a problem with a decent quality MMO mesh.

As for cutting, the best I've found is a metal-cutting bandsaw, or a wood cutting bandsaw if you can find a really fine toothed blade. The next choice will be a jig saw, again with as fine a toothed blade as you can install. An angle grinder will definitely work, but watch out for excess heat, and wear a dust mask.

After cutting, it will be burred, and a benchtop sander is handy to clean it up.

One last way to possibly cut it is with powerful aviation shears, or maybe potent wire cutters, working each of the mesh components individually. It'd be slow but decently clean.

For welding, it can be welded, but the only form of welding I've tried other than spot welding is TIG. To do a good TIG weld requires a respectable machine that can hold an arc at a low current. My very first anodes I TIG welded, and they did warp a bit from the heat. Not pretty, but functional. Try to protect the surrounding areas and back of the weld with argon as much as possible, and I'd definitely scrape the MMO at the weld spots, and wear a fume mask.

You can use Ti wire as fill, or possibly a section of the MMO mesh taken apart and stripped of MMO with a sand blaster or similar. Or use tin shears to cut a really fine strip of Ti from a piece of Ti sheet. Ti welds much like stainless steel. It's hard to make aerospace quality welds, but very easy to join just for mechanical connection and current flow.

Given the cost of the laserred mesh, I've always thought you could cut the anode AND SHANK from the same piece of material... no welding required.

dann2 - 4-9-2009 at 17:19

Hello,


"...........At the other end, install a plastic plug inside the tube,............."

Just wondering would this leak if the plug is not a perfect fit and allow salts to slowly creep up the inside of the tube to your connection. Perhaps pouring some resin (or something that will set) into the tube would do instead if you do not have a piece of plastic dowl of the exact correct diameter.
The compression fittings are a nice professional touch.

You could put a large amount of spot welds on the flattened tube (effectively a continous weld) end and perhaps that would seal it instead of plastic plug.

I often wondered would a few Ti bolts do instead of the welds to connect the Anode to the Anode shank? Would the junction between the Anode and the shank form an Oxide coating that would stop current flowing? Ti bolts can be had on ebay.
Might suit those who do not have a spot welder.

Dann2


[Edited on 5-9-2009 by dann2]

watson.fawkes - 4-9-2009 at 19:27

Quote: Originally posted by dann2  
I often wondered would a few Ti bolts do instead of the welds to connect the Anode to the Anode shank? Would the junction between the Anode and the shank form an Oxide coating that would stop current flowing?
Basically no, for the exact reason you mention.

The more complicated answer is that it would work if you had geometry at the point of contact that made an oxygen-excluding contact, such as a specially toothed washer that pierced both conductors. The high pressure formed by the combination of a piercing point and a bolted connection can be sufficient to exclude oxygen. The problem with just a bolt is that the pressure at all the points of contact just isn't high enough.

12AX7 - 4-9-2009 at 20:21

I bolted copper to titanium anodes. The copper corroded and the bolts rusted but it kept on dumping amperes just fine.

Tim

watson.fawkes - 5-9-2009 at 05:52

Quote: Originally posted by 12AX7  
I bolted copper to titanium anodes. The copper corroded and the bolts rusted but it kept on dumping amperes just fine.
I still worry about long-term function, but I doubt that matters, since you can just recondition the contact faces if they fail. Your note points out to me that my comments are specifically for the "never think about again" scenario, which may be overengineering for a hobbyist-level apparatus.

All said, I still prefer welding.

dann2 - 5-9-2009 at 13:30

Hello,

Welding is definately the best job. It is probably the only way to do the job properly.

When you say that you "bolted Copper to Ti Anodes" I presume you meant it was all above solution surface (obviously). When you go under, things get difficult and the Ti passivation (at contact point) now makes the whole idea unworkable.
When joined by a bolt (under the solution surface) the Anode shank at the point of contact is an Anodic surface (bare Ti remember) where you DO NOT want it to be Anodic. The MMO, at the point of contact with the shank is a Cathodic surface.
My own opinion is that the Ti shank will passivate at the point of contact BUT perhaps it will not? I would be inclined to put my money on the fact that it will but not my bottom Dollar. You could seal the joint but this would be very difficult to do and you would be back to square one messing with sealents etc which never seem to work medium to long term anyways.

Dann2

shank.GIF - 3kB


[Edited on 5-9-2009 by dann2]

Swede - 6-9-2009 at 06:42

If the question is, bare Ti in solution on the anode side, I have never had the slightest problem. All of my fabricated anodes have a bare Ti strap at the weld spot, and the worst they suffer is a bit of unidentified white smut. They do seem to passivate effectively. I am not 100% sure that commercially pure is required. The alloys might be fine. But the Ti alloys are much harder to work than the pure stuff, and I suspect the tendency of the alloys to crack will be much higher.

Commercially, sheet MMO is cut and installed into pool chlorinators and the like without recoating the cut edge, and the electrical contact leading to the cut sheet is plain Ti. So if they do it commercially, I think we're OK, and observations confirm this.

I definitely over-engineer, but I also try to think of ways that improvements can be done when tools like lathes and spot welders are not available. I chose the plastic plug because for me it would be easier, but some sort of poured resin would be satisfactory. My gut feel is that the flattened end of the tube, once welded, is not going to allow much trespass of liquor, but it has a tendency to find its way into the tube regardless, so I'm thinking you may as well drill a pair of 1/16" or so drain holes in the shank so that you won't have trapped liquor for weeks while the anode is in storage.

One method to make a mechanical connection that might work would be a pair of Ti bolts, a strap, another small sections of moderately thick Ti sheet, and you form a clamp-sandwich with the MMO between the strap and the other Ti piece. Drill through all 3 layers, and torque the bolts down to 90% of yield. I think you'd get enough deformation of the mesh and the Ti sheet to form multiple contact points that should exclude liquor or oxygen. Everything would need to be abrasively cleaned and degreased just before assembly to strip the oxide layer. It might work, but the torque required would need to be very high, I think.

Even small towns have professional weld shops. I'll almost guarantee you could find a guy who will weld 2 or 3 anodes/cathodes for you over a lunch break for little money. Professional TIG welders are wizards with their tools. I've seen a guy TIG weld two razor blades at 90 degrees, and another weld two beer cans together.

Swede - 1-10-2009 at 14:41

I am about 1/2 done on a "How To" document on the basic chlorate process for the amateur. It is at 45 pages now and will include much info from here and dann2's site - not copied verbatim but simply incorporated into the doc in my own words and within my own experience. When it is done, I'll convert it to PDF and hopefully some guys will find it useful.

I did some additional experimentation with the n-phenylanthranilic acid (NPAA) chlorate detection test. Of all the things I've done within this discipline, I think I am proudest of this simple test, a 2-dropper bottle cold test for the presence of chlorate contamination within perchlorate.

The original test called for NPAA (a grey powder with the texture of corn starch) dissolved in sulfuric acid. The improved test was 3% tincture of NPAA in 99% isopropanol, and a separate dropper bottle of concentrated sulfuric to acidify the precipitate and develop the purple color. It turned out to be reliable and easy to do.

For the new test, I tried methanol and ethanol as carriers of the NPAA, and at lower concentrations, and other acids besides sulfuric. The best combination was 2% NPAA in methanol, and plain HCl to develop color. HCl is superior to sulfuric in that it is easier to obtain, and colorless, whereas crude sulfuric often is dark and also more dangerous to handle.

To test, a pinhead (less sample is better) of the sample is placed in a test tube, 2 drops of water added, and swirled. 3 drops of the NPAA tincture is added. A grey/white precipitate forms. Concentrated HCl is added dropwise, and 5 to 10 drops will strongly acidify and bring out an unmistakable purple color when chlorate is present. 3 drops of the 2% tincture will detect 0.03 grams per liter chlorate; 6 drops will detect 0.01 g/L chlorate, or 10 PPM. More NPAA makes a more sensitive test, but for everyday use, 3 drops is adequate.

ANY purple color indicates the presence of chlorate. A good quality commercial perchlorate sample will have no color, and remain white or possibly a very slight gray coloration. If you can find a source of NPAA, 10 grams will last a lifetime and should cost no more than $10 or so. It's not an expensive chemical, simply hard to source. Polyethylene dropper bottles are great to make a test kit, or you can simply use a pair of traditional amber glass bottles with dropper caps.

I cannot imagine 10 PPM chlorate causing problems with a batch of perchlorate in terms of pyrotechnic sensitivity. If you clean your perc with SO2 gas and it tests clean, use it with confidence.

dann2 - 2-10-2009 at 03:05

Hello Swede,

Looking forward to reading the doc.

I have still not gotten around to some the Lead Dioxide stuff put I am getting there. Intend to make a good Anode.
I think the notion that LD will stand up to a non-pH controlled cell all the way from Chloride to Chlorate to Perchlorate is a bit of a pipe dream. The pH probably needs to be contolled to keep erosion at a sensible level.
Or probable better to keep the precious LD (all the trouble of making) for Perchlorate making only.

Then there's always the Tin Oxide + Bismuth Anode to be checked out.

Dann2

Crest21 - 5-10-2009 at 02:14

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.

Regards

Crest

_____
dossier surendettement

Swede - 5-10-2009 at 07:02

dann2, I am definitely reserving any likely LD anodes created for chlorate --> perchlorate only. I have committed myself to potassium, which forces a two-step process (Cl to chlorate, harvest/clean, chlorate to perchlorate) due to the crappy solubilities.

I am communicating with a very knowledgeable guy on APC who is going to attempt a one-pass system - a KCl reservoir will feed a small, possibly insulated electrode cell (similar to what I tried except mine recirculated), which will in turn feed a chilled crystallization/collection chamber.

I thought about the math behind this concept. A typical KCl starting liquor will be 14% chloride ion, or 4 moles of chloride. Most guys will terminate a run at around 8%, or 2.25 moles chloride, thus converting 1.75 moles of chloride to chlorate. At 161 Ah per mole, to convert a liter would require 282 Ah.

Let's say your electrode chamber can run at 60 amperes. Therefore, a flow rate of 60/282 = 0.21 liters per hour (assuming 100% efficiency, bulk conversion) should have the effluent at 8% chloride. Upon chilling, the xtals would rain out in the collection vat.

If we assume 60% efficiency, then the flow rate drops to 0.128 liters per hour, of 128 ml/hour. A peristaltic pump could do this easily. It is an interesting thought and something that I have never attempted. At such a low flow, heating could be a real problem. Inevitably, too, you would have some xtallization inside the EC despite the high temps, so jamming of the EC with xtals might be another problem.

The effluent port would need to be placed above the electrodes, be wide-bored, and well-insulated to prevent premature crystallization. The fumes from the collection vat would need to be properly vented, or the room would become uninhabitable.

Overall, there are technical issues to work out, but it would be very interesting to give such a device a try. The enormous advantage would be the fact that you could have a 100 gallon KCl reservoir, power the system on, collect chlorate as needed, then power off.


[Edited on 5-10-2009 by Swede]

hissingnoise - 5-10-2009 at 07:31

Quote: Originally posted by Swede  
I have committed myself to potassium, which forces a two-step process (Cl to chlorate, harvest/clean, chlorate to perchlorate) due to the crappy solubilities.

Why not NaCl Swede? It has advantages over KCl besides better solubility. . .

Swede - 5-10-2009 at 07:51

Quote: Originally posted by hissingnoise  
Quote: Originally posted by Swede  
I have committed myself to potassium, which forces a two-step process (Cl to chlorate, harvest/clean, chlorate to perchlorate) due to the crappy solubilities.

Why not NaCl Swede? It has advantages over KCl besides better solubility. . .


You know, I have never adequately answered this question beyond a sort of lame "no worries about Na contamination for pyrotechnic use." I started with it because it is easy to separate and clean the potassium products due to decreasing solubility, and made up for the solubility issue with raw cell volume.

Straight K does make recycling easier. Wash water and used liquor is good to go after recharging with chloride, while executing a conversion is going to leave a hash of potassium and sodium ions behind.

But the reality is, I have no good answer beyond that I am comfortable with it.

hissingnoise - 5-10-2009 at 08:50

Each to his own, I guess. . .
With K though, you could have a situation where the oxidised salts precipitate onto your electrodes, adhering in large crystals, with a potential to damage your hard-won LD anode. . .
IIRC, sodium seemed to be less erosive than K on graphite.
And I never had a noticeable problem with Na contamination.

astroturf - 15-10-2009 at 13:22

swede wrote:
Quote:

I had a PM from a nice guy in Australia who had his eBay MMO cut with a cutoff disk, and he said they now have a POTENT smell that gave him a headache. I found this to be really odd. Any theories?


that nice guy is me!!! Thanks swede :)
The smell went away after about 2 weeks. I think the smell was due to the anodes being cut with the abrasive wheel probably immediately before being put into the bag for postage. I could cut a bit of anode to test this.

Since then I have cleaned a piece in HCl and used about 6" submerged in a KCl cell at 30A with a PC power supply. It works well.

Swede - 21-10-2009 at 12:03

Hi Astroturf! Good to hear from you!

I have been haunting eBay, and the Laserred material is apparently gone - or, he is sitting on a hoard, and waiting a bit to let the market "recharcge." For those that have some, I would really recommend cleaning by soaking in concentrated HCl for maybe 15 minutes. There is definitely some sort of smut on there that turns the HCl bright yellow, and while I have no idea what it is, the potential for toxicity certainly exists.

What metal ions would dissolve in HCl creating a bright yellow coloration? Any ideas?

tentacles - 21-10-2009 at 18:28

There has recently been some discussion on the passfire board, reminiscing about the somewhat legendary Swedish perchlorate. It is known to be the absolute best perchlorate in pyrotechnic compositions - particle size shape and distrubution just perfect. At any rate, someone mentioned a typical 1992 assay:

99.8 % KClO4
0.03 % KClO3
0.01 % KCl
Insolubles less than 0,01 %
Moisture less than 0,02 %
Neutral pH
Particle distribution: 100 % passing 140 mesh, 65 % passing 230 mesh and 45 % passing 325 mesh.

It is purely anecdotal, but clearly swede's under 10ppm would be very suitable for pyrotechnic use. Here's something a LOT less anecdotal:

Barium and Chemicals and Hummel both distribute military spec. product and that potassium perchlorate spec. hasn't changed since at least Sept. 1962 and perhaps the early 1940s: It's not a hard spec to meet; purity of only 99.0% and 0.1% KClO3, -0-% hypochlorites with easily met particle size standards:

http://www.tpub.com/content/MIL-SPEC/MIL-P/MIL-P-217A/

Swede, there has been some comparison testing between the various brands of perc, it might be interesting to send Dan C a sample of yours to add to the test as an example.

Sedit - 21-10-2009 at 18:47

Quote:
What metal ions would dissolve in HCl creating a bright yellow coloration? Any ideas?


When I dissolve rust in HCl it creates a bright yellow solution. It turns greenish as it gets more concentrated. Possibly some form of iron oxide contamination.

Swede - 23-10-2009 at 07:02

Sedit - I think you nailed it. The smut on this MMO is definitely brown, and pretty tenacious except when immersed in HCl, whereby it comes right off, leaving clean MMO behind. It's good to know it's probably iron and not something nasty like cadmium, lead, or chromium.

Tentacles - Awesome information! The "official" permissible amount of chlorate was always something I wondered about. 0.03% chlorate is LOW. The Hummel figure of 0.1% to me seems more typical of what you'd find in a bulk, industrial process, and my own limited intuition says that 0.1% chlorate is safe; the product can be considered perchlorate for pyrotechnic purposes.

That mil-spec page also has some excellent info.

I would love to have some of my perchlorate analyzed... and would gladly pay a reasonable price to have it done. Is Dan C. on Passfire? Does he have access to analytical equipment?

tentacles - 23-10-2009 at 17:42

Not much of an analysis; more empirical testing. He's done a series of tests comparing various perchlorates in whistle rockets. Remarkable how much difference there is. He's only done some preliminary testing so far, but I think he was planning on getting into it more this winter. It's Dan Creagan on passfire.

http://www.wichitabuggywhip.com/fireworks/rockets/preliminar...

Have you thought of checking with a uni lab dept, maybe some students would be gung ho to do some testing? If not, a prof may be able to hook you up.

Swede - 25-10-2009 at 08:10

I'll look into it. I'll bet there are companies or universities that would do it at a decent cost.

On the tubular electrode shank concept - one thing that concerned me was heating. At 60+ amps, pure Ti heats pretty badly at typical cross sections of 25 mm^2. A 1/2" dia (12mm) OD Ti tube with an average wall has a similar x-section, and will heat up in much the same manner, with the tubular section being more difficult to affix to a heat sink vs. a strap, making it more difficult, and with the very real possibility that the Ti tube will melt or deform the compression fitting that carries it.

I had a thought, and perhaps a solution. #2 or #4 Cu welding cable has an OD, when stripped of its jacket, such that the Cu bundle can be inserted into the tubing to carry the current. With the bottom flattened and welded shut, similar to this picture:



It should be leakproof. From the top, open end, insert the Cu bundle with some force, creating a chisel-shaped deformation at the bottom where the Cu is near the anode. Now, you cap the Ti tube with brass, bronze, or Ti, and the Cu bundle is internally filling the hollow void, with vigorous contact on the walls and cap. You have instantly created a Ti tubular shank capable of carrying a couple hundred amps with little heating. :D

Of course, the Cu will be 100% protected. Another option - use Cu round bar as an insert for 90% of the length of the Ti tube. At the bottom, fill it with stripped Cu cable, or even jam in some Cu or bronze wool, very tightly. You'd get the same effect. Think of the Ti tube as simply an insulator jacket for the Cu, rather than as a primary means to carry current.

watson.fawkes - 25-10-2009 at 09:20

Quote: Originally posted by Swede  
Another option - use Cu round bar as an insert for 90% of the length of the Ti tube. At the bottom, fill it with stripped Cu cable, or even jam in some Cu or bronze wool, very tightly.
Why not just braze the copper rod in at the bottom? Not difficult, although it might require a special flux to strip oxides off titanium.

dann2 - 26-10-2009 at 10:41


Another option might be to jam in some pieces of Copper at the bottom of the tube and fill up with melted Lead or melted solder.

About the yellow color in HCl. The yellow color that is sometimes in hardware store HCl is Iron contamination (I have read).

Dann2

patsroom - 6-11-2009 at 16:37

Hello to everyone, I was invited by one of your members to this site as I have some (hopefully) some exciting news. I found a company that will sell to me Lead Dixoide Anodes at a size that will be useable in the home lab. If all goes well with this deal I am making I could get them out to the those how are interested in having one. But I do need to know if there is a strong interest in abtaining them from those that are willing to buy one.
The following I place on another web site as to try and get a response.
I have been in talks with a company that is welling to sale me Lead Dixoide Anodes. The New Price that they well be to buy one is $135.00 USD plus shipping and handling for type A anode and for type B the asking price is $105.00 USD plus shipping and handling. I would still have to buy a minium of 20 of them at a time. This is for the first order as they wish for the samples to be seen. I do not known if they would increase the price after but I would think not (I hope not).
I need the help of all of the members here to see what you think about this, please reply good or bad so I can decide if I should buy 20 or more.
My feeling is that the price is now so much better (than the price for Pt. coated Ti. at $80.00 to $90.00 for a .5" x 4" with a 3" hanging strap). And theses lead dixoide anodes well do everything that we could want from chlorides to pre-chlorates of the salts.
I know that there is a thread within this forum that deals in the sale of pyro items, but as you can see this is not items for sale at this time. This is a request for replies to see if this is a deal that everybody would be interested in. Like I said earlier I just think that this is a great buy and the price is now so much better than their first go around.
There is not much more I can add with out Beating a Dead Horse on this one. Just one more kick at the horse I just can't help it- This would be a great deal I know it would be.
This was my first offer recieved, But I found the price way to high. Then I got the next offer and felt that it was a price I could work with. I hope to get a PDF in here as well to shown the size.
XXXXXXXX-XXXXXXXX-XXXXXXX
Titanium Products and Equipment Manufacturing Co.,Ltd Price list

Date of offer: October 24, 2009

Item :Lead dioxide coated Titanium Anode

Client name: Patrick

Email:

Address:
Item 1

Type A anode

Cost of material

36USD/piece

Cost of coating

152USD/piece

Unit price

36USD+152USD=188USD/piece

Quantity

20pcs

Total value

188USDX20=3,760USD

Item 2

Type B anode

Cost of material

28USD/piece

Cost of coating

131USD/piece

Unit price

28USD+131USD=159USD/piece

Quantity

20pcs

Total value

159USDX20=3,180USD

Remarks:

Quotation mode

CIF Oregon (Door to door)

Validity of offer

Within 20 days

Minimum of order

20pcs for each item

Coating contents

Lead dioxide(PbO2)

Thickness of PbO2

1.5mm

Lifespan of anode

=2.5 years

Delivery time

Within 3 weeks against Copy of Remittance

Packing

Export Standard Wooden case

Terms of payment

By T/T, 100% payment in advance against Proforma Invoice

XXXXXX-XXXXXXX-XXXXXXX
XXXXXXXX Products and Equipment

Manufacturing Co.,Ltd

Contact person: (Sales Manager)

Tel: 0086+512+6665 XXXX

Fax:0086+512+6536 XXXX

Mobile:0086+151 9568-XXXX(24hour)

Web:

www

Mail

Sorry about blank out the contact infor. I just don't want to sour the cream.

So the price will be $135.00 USD plus shipping and Handling to your door for the large one and $105.00 USD plus shipping and handling for the smaller one. I would love to hear what others are thinking.
I Than all of you if you manage to read this far and I hope to hear from those how would like me to finish the deal........Pat


Attachment: Drawing PDF Anode.pdf (11kB)
This file has been downloaded 476 times


Swede - 15-11-2009 at 10:08

Quote: Originally posted by dann2  

Another option might be to jam in some pieces of Copper at the bottom of the tube and fill up with melted Lead or melted solder.

About the yellow color in HCl. The yellow color that is sometimes in hardware store HCl is Iron contamination (I have read).

Dann2


Dann2, after much thought on tubular anodes, I think your idea is best. Create a hard Pb alloy, plenty of antimony and/or tin, fill the tube (after crimping and welding at the bottom) with the molten alloy, and after cooling, drill and tap the end for whatever bolt you'd like, preferably a coarse pitch. 1/4" X 20 would be excellent to hold the power lugs.

This does three things: It solves the power cable attachment problem, the Pb carries the bulk of the current rather than the Ti, and it does away with any specialty tools like a lathe. All you need is a drill and a tap.

tentacles - 15-11-2009 at 14:37

I finally got around to welding up a round shank anode- noone will remember but I was trying to use solid Ti rod (.625") with a flat milled on it. I had very good success today spot welding the mesh to the rod after preheating the rod with a torch. Not sure precisely how hot I got the rod, but I saw good penetration under the spots I welded.

Swede - 16-11-2009 at 06:50

Good deal Tentacles. Because Ti is slow to transmit heat, a lot like stainless, you can get a nice localized heating that definitely helps with the welds. I've been using an area of slightly greater than 1 square inch for attachment of the mesh to the shank, and I think that should be adequate for anything up to 100 amps.

Got any pics? :)

Bikemaster - 16-11-2009 at 09:24

For the people who miss the really cheap mmo!!! laserred is now alive:P

http://cgi.ebay.com/EXPANDED-TITANIUM-MESH-STRETCHED-SCREEN-...

bbartlog - 19-11-2009 at 12:00

Would it be possible to use an electrically conducting ferrofluid as an anode (see for example US patent 4604229 for a description of how to manufacture such a fluid)? It seems like the resistance might be too high (in the patent the example they give has a resistance of 100 Ohms/cm), but I imagine that anode geometry, like the use of a thin layer floating at the bottom of a cell, could address that. Just seems like certain problems of anode wear and/or blockage by oxidation products might solvable if a fluid anode could be used (like mercury, but in this case a magnetite/graphite particle mix).
Of course it's possible that the surfactants, fluidizers and so on would be too vulnerable to chemical oxidation in this situation.

watson.fawkes - 19-11-2009 at 17:36

Quote: Originally posted by bbartlog  
Of course it's possible that the surfactants, fluidizers and so on would be too vulnerable to chemical oxidation in this situation.
Even the magnetite might be subject to oxidation. It's in a mixed +2/+3 crystal structure. I can't imagine that the +2 iron wouldn't get oxidized to +3.

hissingnoise - 20-11-2009 at 08:13

Magnetite was used, and may be still, as anodes for the production of perchlorates.
It's rate of disintegration is higher than that for LD and its conductivity is on the low side but it was, at one time found to be fairly economical on the large scale. . .

dann2 - 20-11-2009 at 18:43

Hello and good afternoon Sir Hiss,

Quote: Originally posted by hissingnoise  
Magnetite was used, and may be still, as anodes for the production of perchlorates.
It's rate of disintegration is higher than that for LD and its conductivity is on the low side but it was, at one time found to be fairly economical on the large scale. . .


Where did you read that piece of (totally erroneous) information?

Dann2

hissingnoise - 21-11-2009 at 11:29

Well, Well! If it isn't our "little chlorates uber genius" from down-under!
Just for you, here's the appropriately titled; "Idiot's Guide"!

http://www.warezwally.com/files/Potassium%20Chlorate%20Guide...

And in case you can't find the word magnetite there. . .

http://www.pyroguide.com/index.php?title=Preparing_chlorates











[Edited on 21-11-2009 by hissingnoise]

[Edited on 22-11-2009 by hissingnoise]

bbartlog - 21-11-2009 at 16:24

Just searching Google Books for 'magnetite anode' will give some results that should (in aggregate) be pretty compelling, if for some reason you don't find Wally and Wikipedia convincing (which would be understandable).
Anyway, I suspect that the relative difficulty of making ferrofluid compared to making a solid magnetite anode the size of a brick means that a liquid anode of this type would be merely a curio -


bbartlog - 21-11-2009 at 16:24

Just searching Google Books for 'magnetite anode' will give some results that should (in aggregate) be pretty compelling, if for some reason you don't find Wally and Wikipedia convincing (which would be understandable).
Anyway, I suspect that the relative difficulty of making ferrofluid compared to making a solid magnetite anode the size of a brick means that a liquid anode of this type would be merely a curio -


All you need is Magnetite (me foot)!!!!!!

dann2 - 21-11-2009 at 17:32

Hello,

Tutt Tutt!!
Terrible language.

Have you any references that show Magnetite was ever used "fairly economically on a large scale" to make Perchlorate, as you stated?
The refs. you give are a verbatim copy of the Geocities site (no mention of making Perchlorate in any sensible fashion with Magnetite), and the other ref. is a verbatim copy of Wouter Vissers site on Chlorates/Perchlorates. He simply states that you can make Perchlorate with Magnetite. As we all know you can make the stuff (Perchlorate) with DSA, Graphite, IRON!, Lead metal, Cobalt Oxide, Tin Oxide, ............but in a fashion that is of little or no use to us.


Some info. here if anyone is interested in Magnetite Anodes.
See also GB 850,380 where it states that Magnetite will make Perchlorate at a current efficiency of 4 to 5%. Not very economical me thinks!!!!!!!!!




Primary refs. would be nice, in fact they would be fecken great. I think I speak for lots of folks in here when I say that we are all very interested in making Perchlorate, with Magnetite, in a fashion that could be described as economical (thats economical for us, a much easier target to hit than what industry would demand).

You need to calm down Hissing noise. If you continue to yield that sword Seaside Windmill in your usual wild and frothing-at-the-mouth manner, y'll put yer own eye out.
Stop sending me U2U's as I don't read them (when coming from the 'Hissingnoise' instance anyways) as they are inclined to be a bit rude :o

Dann2




sw.jpg - 2kB

Xenoid - 21-11-2009 at 21:03

Hissingnoise (what an appropriate moniker) - quit the bad language and abuse and put up or shut up with regard to the magnetite anode for perchlorate!

The "references" you quote above are nothing more than abbreviated rehashing of information on Visser's and Dann2's sites.

A perusal of the "Perchlorate Monograph" (Perchlorates their preparation, manufacture and use, Ed. Schumacher, 1960) reveals the only mention of magnetite anodes for perchlorate to be a study by Ullmann in 1929 in which it is found to be unsatisfactory and only lead dioxide (with the exception of various forms of platinum) was the only suitable alternative to pure platinum.

hissingnoise - 22-11-2009 at 02:12

Ok! So you guys think magnetite was never used successfully to manufacture perchlorates---is that it???
You really think that every manufacturer went out and bought sheets of polished platinum every time they wanted perchlorate?
And I apologise dann2, for the rudeness---next time I'll be less rude.
And Xenoid (strange name for a silly goose?), consider my puff-adder behaviour under reconstruction. . .




dann2 - 22-11-2009 at 07:55

Hello,

Quote: Originally posted by hissingnoise  
Ok! You really think that every manufacturer went out and bought sheets of polished platinum every time they wanted perchlorate?

No, we don't. We know they also used Platinised Ti, alloys of Pt + Ir and Lead Dioxide.
Quote: Originally posted by hissingnoise  
And I apologise dann2, for the rudeness---next time I'll be less rude. And Xenoid (strange name for a silly goose?), consider my puff-adder behaviour under reconstruction. . .

You don't actually think I take it seriously? :D It IS noisy though. If you could make an effort at being less pre-teen so as to lessen said noise.

Where are the ref's, or do we take the statement, "Perchlorate's were made fairly economically on a large scale with Magnetite", as just some more Hogwash.

Dann2



hissingnoise - 22-11-2009 at 12:31

Magnetite anodes were big (large-scale)!
I never said perchlorates were produced in large quantity. . .

dann2 - 22-11-2009 at 12:57

Hello,

Quote: Originally posted by hissingnoise  
Magnetite was used, and may be still, as anodes for the production of perchlorates.
It's rate of disintegration is higher than that for LD and its conductivity is on the low side but it was, at one time found to be fairly economical on the large scale. . .


Have you any refs. to back up the claim above irrespective of the interpretation put on it.
Refs. please (ie. get a move on).
How big were the Anodes, who/where were they made and used. Where did you find out or learn of these 'facts'. If you don't have any refs. to back up the claim (irrespective of the interpretation) I, (and I suspect others too!) will be presuming that both the claims that:
1)Perchlorate was made on a large scale with small scale Magnetite Anodes and found to be fairly economic or
2)Perchlorate was made on a small scale with large scale Magnetite Anodes and found to be fairly economic
(ROFL)
are indeed more Hogwash.

If you have no independent refs. you can always simply state that you have no independent refs. to back up the claim. I don't believe you, your taking the piss.

Dann2

Lord help us all if the Perskovites appear :(

[Edited on 22-11-2009 by dann2]

hissingnoise - 22-11-2009 at 15:53

I don't have a lot of free time since I've seen off a harmless but persistent rhinovirus, but when I find irrefutable evidence you'll be one of the first to know---rest assured. . . !

dann2 - 22-11-2009 at 17:37

Hello,

From above:
_________________________________________________________________
1)Perchlorate was made on a large scale with small scale Magnetite Anodes and found to be fairly economic or
2)Perchlorate was made on a small scale with large scale Magnetite Anodes and found to be fairly economic
__________________________________________________________________

Whatever you do, don't forget you are looking for info. on option 2 (as stated by yourself). Large scale Anodes (great big monster Magnetite Anodes or a large amount of smaller ones) employed in a cell for small scale Perchlorate production. (LOL)
I'd wheel out the rolleye's but since you battleing with the common cold I will make an exception.
Good Afternoon.
Dann2

[Edited on 23-11-2009 by dann2]

dann2 - 16-12-2009 at 15:40

Hello,

@Swede. There is a Bi Oxide + SnO2 Anode in the patent below (example three). It claims that it is useful for Chlorate and Perchlorate production. It has not been tried before (patent was posted elsewhere on the board at some time or other). It would definately be worth a try. It's a no Lead, baked only, possible Perchlorate Anode.
You will need hot HCl to etch Ti, SnCl4 (liquid) and Bismuth Nitrate.
You could probably use SnCl4:5H2O (a solid) and dissolve it in Alcohol + some conc. HCl. You could perhaps use Bismuth Chloride if you cannot get the Nitrate.
You just brush on the solution to the Ti and bake. Put on about 6 coats (or whatever you wish).
Might be a break through!
SnCl4 (liquid) or SnCl4:5H2O (solid) can be had easily enough on ebay.com. You only need small amounts.
I tried using a Tin Oxide + Antimony Oxide Anode in a Perchlorate cell (pure Na Chlorate dissolved in water) for approx. 19 days. The solid extracted after that time contained 69% Chlorate the rest was Perchlorate. Not a useful Anode but the Tin Oxide held up well for the 19 days. It would have lasted much longer IMO but I put it into a Lithium cell and the Lithium cell seemed to erode it rapidly in approx. 24 hours. I was not really trying to make a Perchlorate Anode from Tin Oxide + Antimony Oxide Anode just testing my coating/coating method to see how well it held up in a Perchlorate cell as I was going to use it as an undercoat between Ti and LD.
There is a thread here on the Anode I was testing: Tin Oxide + Antimony Oxide Anode.
If you have an oven (you have) it is quite simple to do.
Keep it KISS. Don't be tempted to go down the 'Johnny Fortycoats + half the elements in the Perodic Table' road! (sorry about that :P)

Good Luck
Dann2




[Edited on 16-12-2009 by dann2]

Attachment: US 4272354 Bismuth_DTO perchlorate anode.pdf (253kB)
This file has been downloaded 584 times


DuPont Elvanol 71-30 100% hydrolyzed PVA thickener

Rosco Bodine - 16-12-2009 at 19:02

http://www.chemicalstore.com/navigation/detail.asp?id=PVOH2

You could actually use a very small amount of the antimonate
for example 1 or 2% of the total weight of the principally Bi doped DTO composition. Sb reportedly functions to decrease the grain size and densify and toughen the coating as well as to increase the oxygen overvoltage, which are desirable and should enhance the anode coating durability. The hydrosol precursor should yield a much higher quality DTO baked film than what is gotten from other precursor schemes, and it should build thickness faster for a series of baked coats. For the first several coats it would probably be best to stick to the lower ~10% doping levels which result in an optical quality pore free sealing film, in order to create a dense barrier layer protecting the substrate. A higher doped but less mechanically perfect, yet more catalytically active coating can subsequently be applied as the working coating. The additional doping could be achieved by using the higher levels of needed Bi in the form of a soluble complex of Bi added to the hydrosol, if indeed it is not practical to simply raise the percentage of Bi in the described hydrosol.

This is a higher art for producing tougher baked coatings
than is likely to be achieved using chlorides precursors.

Oxalic acid is going to be a superior etchant for bare Ti.
There are a couple of reasons why oxalic acid is the preferred etchant. The surface effect has a physical property which enhances adhesion of coatings. And there is a trace residue of Ti oxalate at the interface which on baking supplies carbon from charring and has a reducing effect upon the TiO2 formed at high temperature, resulting in a conductive mixed Ti oxide at the interface which is also more capable of adsorption of dopants. For these reasons, it is
justified to prefer oxalic acid as the etchant.

And a Co spinel or a mixed Co/Ni spinel would probably make a superior interface coat as the first baked primer coat,
one or two coats only, followed by the DTO.

In the famous words of Yogi Berra,
"This is like deja vu all over again" :D
Attachment: US6777477 Bi2O3 doped SnO2 via ammonia soluble derivative.pdf (67kB)
This file has been downloaded 462 times

[Edited on 17-12-2009 by Rosco Bodine]

Xenoid - 17-12-2009 at 22:09

Here's a neat pool chlorinator MMO electrode assembly I recently acquired. It is notable for its unusual design which I haven't come across before.

Firstly it uses solid plate electrodes (140 mm x 47.5 mm) these comprise two monopolar anodes and two monopolar cathodes. Each set of these is connected by a strap at the bottom of the assembly. Between each anode and cathode there are two unconnected bipolar electrodes. There are ten electrodes in total and the total thickness is about 3.5 cm giving an inter-electrode distance of less than 3.5 mm.

All the electrodes are MMO coated and there is no polarity marked on the connectors, this suggests it was run in an automatic polarity switching "bipolar" chlorinator. I thought the design was perhaps quite old but in fact it is date marked 11 - 1 - 2005.

There is a little erosion of the MMO around the edges, but it still appears quite serviceable, I think I will pop it in a chlorate cell and see how it performs. That's about 660 cm^2 of MMO anode in a very compact unit :o

Electrode.jpg - 28kB

tentacles - 18-12-2009 at 08:36

Looks like it may have been removed from service because of that short or near short from one of the plates warping?

Xenoid - 18-12-2009 at 11:13

Quote: Originally posted by tentacles  
Looks like it may have been removed from service because of that short or near short from one of the plates warping?


Hi tentacles - when I saw how the photo had come out I thought someone might mention that! In fact, none of the plates are touching, I don't think that plate is warped from use either. That near 1 mm thick plate is really tough and I think the corner was bent during a sloppy guillotining process - probably made on a Friday afternoon.

Many of these units are removed during routine servicing or for some other problem with the pool other than the chlorinator. The pool contractor makes a nice little profit when they are replaced. Most of the ones I have obtained still have usable MMO. That said, I did come across one that was virtually held together with "salt" encrustations and crumbled in my hands.

I have discovered a slight problem with the one above, the Ti strap is cracked on one side where it is spot welded to the Ti bolt. This damage was caused by the service guy's rough handling when removing the bolts from the plastic lid - which he wanted to retain. I need to get a spot welder to fix it otherwise current handling will be somewhat limited.

dann2 - 18-12-2009 at 12:52

Hello,

Another gem from the dustbin Xenoid!
At 200mA per square cm of actual Anode area in a Chlorate cell, thats 660/2 x 0.20 = 66 Amps for this Anode. You will need to put more connections going to it to carry all that current. When used as a pool chlorinator it carries damn all.
Would perhaps an AC have been applied to it when it was used as a pool Chlorinator?

Dann2

Swede - 20-12-2009 at 09:20

Nice find! Xenoid, if the crack you mention is simply from the bolt hole to the periphery, I doubt it would limit current, especially if you used a washer of Ti or 316 stainless to compress and form a nice connection. If that's not where the crack is, then ignore!

If the crack is elsewhere in the strap, a doubler of Ti could be spot or TIG welded on to carry the current. It is hard to do much work with electrochemistry without some sort of welding apparatus.

When I was corresponding with deNora, they specifically asked if I wanted bipolar mesh; AC capable MMO that is used to self-clean the structure. I said "No, the cheaper DC only stuff is fine for my needs." It lends support to the notion that most of the advanced pool chlorinators made these days, especially those controlled by advanced microprocessor power supplies, are bipolar. I don't know why one would want or need bipolar material for what we do, but it is interesting anyhow.

If you wanted to, it shouldn't be hard to straighten that little warp with a pair of fine pliers.

[Edited on 20-12-2009 by Swede]

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