387 replies to this topic

[sasman]

What metal is the graphite anode conected to?...

I cant understand if that entire anode was submerged then why has it not erroded??.. even at very low currents the metal would errode?..i have tried with lots of different sealers and none last long. even proper stopping off laquer doesnt last long once the corrosion starts it soon spreads?..

That photo must be a "before"? photo...Have you a photo of it after use?.. ..All that green sludge is either iron or copper errosion products..It's one the hardest things to eliminate from a cell...

I like the Photo of those big crystals..my crystal's are very small...What type of yield do you get from that setup..

[gilbert pinkston]

the green comes from dichromate and carbon i think the solution starts out orange when you put the juice to it it turns yellow then eventually green until you add HCl which turns it back to kinda orange for a while then back to green this is how i judge pH don't know how much it tells me but i'll do it till something better comes along......i got the eletrode graphite off e-bay the metal is from a computer chassis so i don't know what it is exactly food cans work just as well they just aren't as straight i'm sure there is no contamination the only thing that shows it is the graphite to a very small degree........ the anode-cathode unit is one piece held together by two screws all metal is a part of the cathode and submerged with the anode so it does not corrode....this pix was taken after at least 3 weeks of operation i used wax to protect the anode to wire connection and have had to redo some.........the wax contracts too much on cooling the reason this one is out is to replace the wax with silicone caulk to see if it works better........the temp is below 40C and the current is less than 40ma per cm2......i ran more current and the graphite did not like it ...the green sludge is NaClO3 crystals there is not as much carbon in there as it looks like i put the sludge in a funnel turn on the vacuum rinse twice with a little saturated salt solution and twice with a little water then it looks good and is clean enough for the O4 cell..........the last NaClO3 i bought was in 100lb drums for $35 but i just wanted to make it myself to see if i could in a reasonable manor........i don't know what kind of yield i get never payed much attention electricity here is about 7 cents per KWH i think that is cheap i am working through a 40lb bag of water softener salt have got ten or fifteen pounds of O3 have about four gallans of satuated salt solution and the rest is in various stages of process in five one gallon pickel jars with plastic two liter soda bottel chemneys on the top to cut down on spray....been at it for four or five weeks

Edited by gilbert pinkston, 25 March 2005 - 07:34 PM.

[alany]

It is interesting that the Cr it is reduced to the trivalent form in the cell. You'd think with all that anodic oxidation going on it would stay hexavalent. It must be being reduced against the cathode, iron is quite a good catalyst of that process, and the hydroxide formation at the cathode would tend to prevent iron dissolving into the solution, I guess that is the whole point of adding chromates to the solution in the first place? It does make one wonder if the protective effect is permanent for the life of the liquor or if the hexavalent chromium has to be replenished?

I've never used Cr before, but I might try two 100 ml test cells in series, one with and one without to compare the effect on mild steel cathodes. Cathodic issues don't worry me too much, the 6Al4V Ti alloy rods I use seem to be completely inert as cathodes. But they do easily erode as anodes, they erode away at any chloride concentration rather than passivating. Curiously they do oxidise manganese chloride to permanganate while eroding away - I discoved this after trying to anodise the Ti with copper and manganese ions in solution to form a primitive MMO electrode - the purple colouration was unmistakable MnO4-. The resulting surface on the anode is interesting, it is grey like cast-iron, but some parts of the anode did anodise, growing a colourful oxide layer (which despite the colour are *not* copper from the solution):

http://nexus.cable.n...anodised-Ti.jpg

On the additive front I've found the sulfite chemicals added to destroy chlorates seem to increase the efficiency when the electrolyte is reused. Perchlorate production in particular seems quite enhanced. It may be being oxidised to persulfate which is ment to increase anode efficiency for perchlorate production. I wonder if sulfur compound build-up is a problem when you recycle the liquor continously?

I just found an Australian site that sells commercial Pt/Ti anodes, yay!

http://www.palloys.com.au/

A little pricy, but just the ticket for a perchlorate cell. I've ordered one, we'll see how it goes.

The Pt/Ir wire anode just about died last night... It got *very* thin near the glass seal. So I stopped the cell. It had just about had it physically anyway, the high temperatures had melted the hot melt glue and it leaked into the cell and ended up floating on the electrolyte. I am wondering if Ozone production rather than Chlorine is responsible for the relatively rapid destruction of plastics used in cell construction...

No luck finding a cheap source of MMO anodes for my big sodium chlorate farm project. I may just have to use high density graphite rods. That would be workable, but I'd prefer a DSA electrode for long life, I want to be able to run this cell at high current densities, temperatures, and 100% duty cycle taking out a litre or two of liquor every few days.

Thought for the day: Don't do the Indigo Carmine chlorate test with almost a pure saturated solution of Sodium Chlorate. The reaction is *violent*. Chlorine Dioxide fizzes out of the test tube blowing a foam of hydrochloric acid across the room. The choaking explosive gas isn't very plesent or safe to have liberated in those quantities either.

[gilbert pinkston]

i know about adding HCl to chlorate it is terrible it can choke you befor you know it if anyone wants to do this they better have a plan to deal with it.....i do it to purify my NaClO4 and it's the worst part of making the stuff the HCl is only $4 a gallon so i would like to be able to do it that way what i am doing now is get just enough water in the cell to keep the O4 crystalizing out continusly but that means the O4 concentration is high and may hurt effency which would slow the process down.......does anyone know of a way to get rid of the O3 without generating any gas....that would be great.........i've started converting some of this homemade NaClO3 to O4 took off my first batch got the flat diamond shap crystals but too much O3 left for me last time i think the cell ran a little too warm too much evaporation i think i should have added water and let it run longer or used a bigger cell volume........back to O3 i think graphite works good i have got about $20 worth of it in my cells i think it will make it thu the 40 lbs of NaCl and be ready for more i just have to concentrate on gettting the O3 ready to make O4......my previous O3 to O4 was with weed killer it worked good i never checked the pH but i did a whole 100lb drum in about five months or so...... with my homemade stuff in the O4 cell the pH is high and there is a chlorine smell the first hours of the run it may go away because the pH goes up or hopefully because there is not much NaCl there to start with....... it ain't easy trying to make this stuff but it sure is fun

[sasman]

100 lbs ..WOW!!... ..What Anode did you use to convert the weedkiller ..and how much current did you use?.and can you remember the Voltage?.. 100 lbs would last me several lifetimes...


Cheers..

[gilbert pinkston]

i used many anodes......PbO2 on welding rods some lasted a week or two most alot less when they failed they made a nasty mess of the electrolyte but when left to settle it all came out and i took the clean solution and put another one in it......i washed the sludge and saved the wash water for the cell and the broken pieces of PbO2.......i went through a fifty pack of rods the anodes were beautiful but defective.........then i thought i've got all these pieces can i use them? i put them in a tube made of screen with a broken anode in top for a connection put them in with only the pieces below fluid level and it worked (somewhat)...........then i invented the pinkston-supermassive-lead dioxide-anode (PAT. PEND.)........i took this arrangement and put it back in the plating bath up past the broken anode........i thought to myself what better substrate than PbO2 itself.......when i took it out a day or two later it was ugly but worked..... i got four going now (in four (electrolytic) gilbert cells ( a P-S-LD-A with a copper cathode in a mason, pickel or mayo jar))at about 4 or 5 amps each i made the P-S-LD-A at about the end of doing the 100 lbs so i don't know how long they last that was last year this year i thought i would try and go all the way from NaCl to NaClO4 starting with graphite finnishing with PbO2.......the P-S-LD-A may be capable of doing this in one step but i don't completely submerge it (only the part that is 100% PbO2) like i do graphite so i may loose a lot of Cl but maybe not.......i'm making some more and when i get extras i may try this but i am satisfied with graphite for ClO3 step.......so far i have had a P-S-LD-A last two months and is going strong.......i never measured the voltage or current i used on the old carbon anodes that would be too much like the scientific methode for me..........it's ok doing it this way you at least get a yield but the dream set up would use Pt in two steps

Edited by gilbert pinkston, 26 March 2005 - 03:08 PM.

[sasman]

Hehe i like the sound of that..

i invented the pinkston-supermassive-lead dioxide-anode (PAT. PEND.)........

How big was it ? ..have you any photos?..When you mention you made PbO2 on welding rods do you mean copper plated welding rods or carbon gouging rods?..Also when you say they failed how did they fail?.. I have made some PbO2 graphite core anodes that are in testing..I will be really Pissed!! Off if they fail after a few weeks.. If they last 2weeks without signs of corrosion i will put them to use..

I coat the graphite with PbO2 just leaving the last 4 cm orso of just bare graphite.. So that the solution wont wick up the graphite core , the coating is about 13 or 14 cm long but i only put in 12 cm of the anode .. I dont use any copper wire in any of the wires or cathodes ..
Copper is bad news when it comes to making ClO4 if you intend to make Ammonium Perchlorate..which is one of my main reasons for making ClO4..(thats another reason why i am running in my Anodes to leech out any copper that may be in the coating as well as any other crappy chemicals..)..

Have you any more photos ..you can show?..Cheers

Cheers

[gilbert pinkston]

sorry for the trouble in getting these pix


graphite chlorate cells http://eseephoto.com...9294_189116.jpg
making a pinkston http://eseephoto.com...9294_189106.jpg
gilbert cell http://eseephoto.com...9294_189112.jpg
PbO2 http://eseephoto.com...9294_189114.jpg
reconditioning the used bath for anodes http://eseephoto.com...9294_189110.jpg

the average pinkston anode is over one pound
copper plated gouging rods i peeled the copper off
i made a few on graphite in some areas the plating was so tight you couldn't force it off but it seemed there would be a place where it would crack and the substrate would erode the PbO2 doesn't erode something gets under and the coating is forced off and then it's curtains
when i use a copper cathode for O4 the electrolyte is perfectly clear when it settles down i don't think it errodes
if you get that GSLD anode to work let me know exactly how you did it
they would be much easier to work with form a physical or mechanical standpoint
i used the spinning methode last year and did rods 18" long that was a trick.....how do you deal with the pinholes? anything special you did or just according to the literature on everything else like temp amps etc.

[sasman]

Very intresting photos gilbert..From the photos of the Broken bits of PbO2 your anodes are very thick?..How thick is the coating?..Also how long do you plate your anodes?...You mention pinholes..Have you any photos of these pinholes?..


I spin the Anodes to stop pits forming...Pinhole,pitting is the reason for Anode failure.. Did you have pits pinholes on your welding rod anodes?..

18" rods now that is big!!!.. How big a diameter were those and were they succsefull?..

( a P-S-LD-A with a copper cathode in a mason, pickel or mayo jar))at about 4 or 5 amps each

4 or 5 amps that seems like a low current for a large anode?..

I will post some of my photos tommorow or maybe later tonight...

[gilbert pinkston]

some of the coatings were 1/4 in thick on i think 3/8 in rod....some i plated for a day or two for a vessel i used either a gallon pickel jar or a one liter graduated cylinder.........i had trouble with pinholes at times they are very small and wouldn't show up in a pix.......i'm not going to spin any more i checked on using surfactant and thought i would give it a try but to order what was called for cost way too much i think $50 dollars or so for 125g i ain't going to do it.......i got to doing some research reading labels and found out that surfactants are used in agriculture and gardening to help herbacides and insectacides so i got some for about $5 (since then i've found a gallon for about $9) i don't know it's total effect on the coating but i haven't had one pinhole while using it that way i don't have to special buy rod shaped graphite i can use any shape piece........... graphite other than scrap is expensive and in my case there is a good chance it was going to fail......the full length of the rod wasn't plated just about 12"..........the good thing about the pinkston anode is you can use the bath over and over the quality of it dosen't seem to matter ......when it's used put it on some more Pb ........it looses some NO2 but also some water from slow evaporation if you use a heated bath so you end up with a good concentration for the next run there is no waste.....a percentage of my plating solution is over a year old i have never changed solutions......i do it my way only because i had so many failures using someone else's way that is why i would be very interested in other experiences........yeah 4 or 5 amps ain't much but my jars get warm and i don't want to over tax my anodes although it's my opinion the pinkston anode will prove itself tuffer than a goverment mule atleast compared to my earlier tries

[sasman]

Ok i think i have cracked making Large Graphite Substrate Lead Dioxide Anodes (GSLD)..If you want to make Chlorate(ClO3) or Perchlorate(ClO4) you can use various Anodes Platinum is the probably the best ...Lead Dioxide (PbO2) is next best...

I have gone for the PbO2 anode because you can run the cell right from Chloride(Cl) to Perchlorate(ClO4)..if you used Platinum to do this then you will get excessive corrosion on the Platinum Anode due to the low Chloride concentration stage..

I tried plating PbO2 on to 13 mm Carbon Gouging rods because they were very cheap and looked like graphite!!.but i found it didnt take the coating very well so i Binned the idea..Graphite works realy well..
I got some Fine grained 10 mm Graphite 500mm long rod Graphite rods

Also after making Good 10mm Anodes i got some larger 32 mm x 500mm graphite rod 32 mm Graphite rods

You need to treat the graphite so that the PbO2 adheres well.. To do this you simply electolyse the anode in a 10% Sodium hydroxide solution i applied 3 volts at about .0.05 Amps per square Decimeter..that works out at about 1.5 to 1.75 amps For the 10 mm Anode and about 6 to 7 amps for the 32 mm Anode..

Anode being etched Close up of etched anode surface

Etching Anode

When electroplating the PbO2 tiny oxygen bubbles form,If theses bubbles are allowed to stay on the coating these bubbles will form pits which will allow the corrosive salt solution through and thus destroy the substrate which in turns destroys the Anode..
In industry surficants are used which eliminates this problem..I spinn the electrode the centrifugal force throws off the bubbles leaving a nice smooth coating...

The plating tank was a 3 litre pyrex beaker .the plating solution was 333 g a litre Lead Nitrate + 50 g litre Copper Nitrate ..To spin the electode i used a Small 240v electric motor from a Fan..Mounted on plank of wood..To lower and raise the electode i used my camera tripod ..

The plating tank operated at approx 60 centigrade i used an electric hotplate with magnetic stirrer to agitate the solution..

Tank set up

Spinning graphite?

Spinning electrode side view....

Here is a close up of the finished product 13 mm GSLD

I tried the electrode in a Sodium Chloride solution and it took 9 amp with no sign of errosion or heating.. So i Started making 32mm anodes..
I had to use a larger electric motor the Small fan motor siezed up when spinning the larger electode..Because the motor wieghed much more i had to use Aluminium bar to mount the motor on ...the extra weight helped reduce vibration..

32 mm In tank

32 mm In tank close up

Close up of Electrode before coating

Close up of Electrode after coating

After plating the tank is replenished with the addition of Lead Dioxide (PbO) a bright yellow powder ..Plating tank with an excess of PbO added i leave it stirring over night then filter the solution.. and leave it to stand for a few days before use so that any nitrites formed (which lowers the plating tanks efficiency).are oxidised back to nitrate..I acidify the solution to PH 1 with Nitric acid and its ready for use.

.I could have used a surficant to eliminate the bubbles, but continued use of the plating tank ends up that the breakdown products of the surficant makes a poor PbO2 coating...and to eliminate the breakdown products required the use of amly alcohol and distillation equipment...
Here are a few more pictures


Some more anodes

Platinum mesh anode

First graphite anode

36 mm Anode made to take at least 27 amps

The 13 mm Anodes can take 9 amps with no signs of errosion so far..its been in the test tank nearly 2 weeks..The 36 mm Anodes has been in testing tank nearly a week and no signs of errosion with 27 amps through it....

The power is supplied for the 100 amp Chlorate cell is a Power Ten P62B 325 amp 5 volt power supply This is rated for continous use and weighs over 20 kg so hopefully should be up to the job..


To be Continued...

[alany]

Wow, that is quite impressive anode work.

So far all I've done it etched a lot of Titanium. I think I should try the lead dioxide way, but your setup is quite a bit better than I could do right now, I don't have a stirplate, its a piece of equipment I've been meaning to build or buy.

Wanna sell me a big anode for my 25 litre cell?

Where did you get the fine grain graphite rods from? I have not found an Australian supplier of high density extruded graphite at a reasonable price. Graphitestore.com is cheap enough, but the shipping is nuts, they only offer expediated air services that cost hundreds of dollars for $20 worth of graphite! There hasn't been a lot of good graphite on eBay lately either.

[gilbert pinkston]

27 amps on one anode is fantastic i am running a total of about 20 amps on 4 of mine and they are nowhere near as pretty......i made a few on gouging rods that lasted a month or so in about 50 attemps one of which i put in the neck of a clear upside down two liter bottle with the bottom cut out and the cathode close to the top after a week or two i could watch the NaClO4 crystalize out as the NaClO3 was consumed the longer it ran the more gas came off the anode and may be a good indicator of how much O3 is left i always used persulphate ...... i'm going to keep making pinkstons until i run out of broken PbO2 (i have about 5 lbs left) and get them prduceing then i may try more graphite or if i could find some 100% titanium not an alloy i may try that ....there is a patent that uses high HNO3 that looked like it didn't need a lot of metal prep .......i would be very interested in the erosion rate in the chloride to chlorate step since someone wrote it is rather high

[Pretty green flames]

Hey, Alan

Any chance that you take a couple of photos of your power supply ?? I'd like to know what to look for when i'm out shopping

[alany]

Nothing special about it, it is a generic 25 A 3-15 V variable supply. It was originally purchased to power HAM radio equipment, it is *way* overkill for the job. Here is a picture anyway:

http://nexus.cable.n...90/p0004239.jpg

Jaycar catalog number is MP3088, it retails for around $350 AUD, but that is a rip-off, you can pick them up on eBay or elsewhere quite a bit cheaper. It isn't a supply I'd recommend for this work anyway. A switcher supplier would be more efficient and capable of supplying higher currents at lower voltages.

I have also been using a 1 A bench PSU for small experimental cells, unfortunately it only has two fixed current limiting settings, 1.2 A and 20 mA. That isn't as useful as fully adjustable limiting, the cell resistance drifts around. It is a nice supply to use though, it is basically indestructible and I can fix it if I do kill it because I built it.

I was looking at my collection of transformers tonight and I think I'll overwind one of the big toriods with some heavy wire and use a variac to control the voltage.

If you want a cheap experimental supply build your own. Halogen downlight transformers are very cheap and capable of 4-5 Amps, they are typically thermally fused and designed to tolerate a short circuit indefinately, limiting the current to around 20 Amps. All you need is a chunky bridge and a large electrolytic capacitor. Use a variac to control the output, or build a linear series regulator from a 3-terminal device like the LM317 or LM78xx and a pass transistor or two on a heatsink. You can bias the COM pin of a LM7805 with a pot and make a very cheap and simple variable supply.

For a constant current supply something like this should work, but I haven't tried buliding it yet:

http://nexus.cable.n...t-regulator.jpg

Kinda primitive and inefficient, but it could be scaled up to hundreds of Amps by paralleling pass transistors. A switcher would be more efficient, but would require more exotic parts.