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Author: Subject: More on PbO2 electrodes
FrankRizzo
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[*] posted on 26-4-2007 at 13:05


Damn, that looks like one my roommate's socks :)

Great job, btw.
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hashashan
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[*] posted on 26-4-2007 at 16:47


well actually the cloth is from a sock ... so there is a chance there ... :)
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dann2
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[*] posted on 28-4-2007 at 07:22


Quote:
Originally posted by hashashan
well actually the cloth is from a sock ... so there is a chance there ... :)


What material is the sock made out off?

Cheers,

Dann2
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hashashan
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[*] posted on 28-4-2007 at 13:14


just a simple thick sock .. it was made out of some kind of cloth
however some bad news, my contact disintegrated.. heated up and a part of the electrode caught fire and burned out. so i think ill try to make a plastic anode from a CD
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hashashan
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[*] posted on 29-4-2007 at 10:17


Hey guys, i am having troubles using this silver paint. can i just use a silver wire instead?
i mean just clip on a silver/silver plated wire?
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12AX7
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[*] posted on 29-4-2007 at 19:17


I use a copper strap and spring clamp for electrical connection to my bar of graphite. It gets a little crusty, but mostly from salt. It's far above the solution, out of the spray and gas for the most part. You need a tall, sturdy electrode for this.

Copper plating may also be a possibility if you don't have silver. The other day I made a suprisingly adherent layer of copper on a spare piece of graphite, from a strong copper and HCl solution (that may have Ni or Fe in it also).

Tim




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hashashan
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[*] posted on 29-4-2007 at 22:38


but i have a cloth reinforced PbO2 anode.... what does graphite has to do with it. i once tried to clamp graphite on it but had way to much resistance.
well i bought a silver wire today, hopefully it will do the trick
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12AX7
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[*] posted on 30-4-2007 at 00:48


C and PbO2 are both ceramics. A clamp works for my ceramic. Maybe it will work for yours? :P

Tim




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hashashan
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[*] posted on 30-4-2007 at 00:54


what clamp?
the problem with PbO2 is that it is a powerfull oxidiser and will oxidise most metals in the point it touches them. Silver has a conductive oxide, thats the trick :)
the problem with bad connection is huge resistance wich leads to low potential (no perchlorate, and even no chlorate) and high temperature wich can and does lead to autoignition of the anode.
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12AX7
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[*] posted on 30-4-2007 at 07:25


I know! Cut a hole in the bottom of a plastic jar, silicone it over the top of the electrode and fill with... MERCURY! :D

Woulda passed in the 19th century, anyways...

Hmm, what kind of heat can that thing ultimately handle, anyway? Fusable metal might be a solution after all...

Silver plating would be nice though, yeah.

Tim




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hashashan
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[*] posted on 30-4-2007 at 07:31


I dont how much heat can it handle, but the bad thing is that its a kinda shitty heat conductor. While i was electrolizing the solution was 50 degrees while the part of the electrode that was over the liquid was on flame :D

silver plating is problematic there.
A new direction i was thinking of is Tantalum, its quite cheap on ebay. anyone had luck in plating tantalum? maybe a partial coating? i mean cloth reinforced tantalum tipped (coated also with the same layer of PbO2) anode?
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[*] posted on 30-4-2007 at 09:07


Quote:
Originally posted by hashashan
I dont how much heat can it handle, but the bad thing is that its a kinda shitty heat conductor. While i was electrolizing the solution was 50 degrees while the part of the electrode that was over the liquid was on flame :D

silver plating is problematic there.
A new direction i was thinking of is Tantalum, its quite cheap on ebay. anyone had luck in plating tantalum? maybe a partial coating? i mean cloth reinforced tantalum tipped (coated also with the same layer of PbO2) anode?


It would be cheaper to use Titanium. Tantalum can be difficult to come by in a shape(flat sheet) that you want.
All valve metals will require a precoat of something that will protect them from the Lead Dioxide. You will need Pt, or Pt Oxide or doped Tin Oxide.
One patent I have seen plated Lead Metal onto Ti then formed a coat of Alpha Lead Dioxide on the Lead by electrolysing in sulphuric acid. Then plating on top with Beta Lead Dioxide (Lead Nitrate bath)

What sort of currents are you putting into your anode. If anode surface at contact is very rough try using graphite paste.

Dann2
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hashashan
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[*] posted on 30-4-2007 at 09:14


i put about 12 amps. the process started like a charm and then something happned .. the contact got crappy and thats it.
nobody answered me, what will happen if ill just use a silver wire, i got a pretty thick one. about 1 mm.
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[*] posted on 30-4-2007 at 13:49


the silver wire doesnt seem to work, neither graphite. What on earth could be the reason? i tried to connect it to a million places, the anode just started to be a crappy conductor. Any suggestions?
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[*] posted on 30-4-2007 at 17:38


You need more contact area. Grind down a smooth spot on the electrode and use sheet stock.

Tim




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hashashan
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[*] posted on 30-4-2007 at 23:11


i tried it all, it just wont conduct ... very weird
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hashashan
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[*] posted on 1-5-2007 at 12:02


And another question,
Did anyone ever tried to grow a massive anode on a piece of Pt?
I am about to receive a piece of Pt, And i thought to grow the anode on it and slowly take it out and grow more, i mean to take it out mm by mm while the last mm grows again,
Actually i want to grow a 30sq.cm anode on 2cm pt wire, possible?
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[*] posted on 1-5-2007 at 13:50


I have to ask the obvious question: have you checked the rest of your power supply? Could the conduction break be somewhere else?



Helicopter: "helico" -> spiral, "pter" -> with wings
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[*] posted on 1-5-2007 at 14:43


Quote:
Originally posted by hashashan
And another question,
Did anyone ever tried to grow a massive anode on a piece of Pt?
I am about to receive a piece of Pt, And i thought to grow the anode on it and slowly take it out and grow more, i mean to take it out mm by mm while the last mm grows again,
Actually i want to grow a 30sq.cm anode on 2cm pt wire, possible?



If you are going to get into the business of growing massive Lead Dioxide anode (like growing an anode by starting with 2 cm of Pt.) you will need a well contolled set up. Good pH control, fearly steady Lead Ion concentration, steady temp. etc etc. Lead Dioxide can be deposited on Pt. It has been done many times when Ti was plated with Lead Dioxide. A thin coating of Pt was deposited first to protect the Ti from the Lead Dioxide.
I was flicking through a library book today and read that Lead Dioxide was known as the 'Poor man's Platinum'. HUH.

You can grow massive anodeS on Iron, Nickle and other wires. It has been done in the journals. The maker started with a close to neutral Lead Nitrate bath and kept plating solution treated with Lead Carbonate etc to neutralize the nitric acid as it was produced to stop it from attacking the Iron, Nickle etc. Well controlled set up.
Can I presume that the plating tank for the 'Sock substrate anode' was a simple affair. This type of set-up will surely let you down if you try to make massive anodes.

What are you replacing the Lead in the tank with as it gets depleated?




DANN2
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[*] posted on 1-5-2007 at 15:32


Quote:
Originally posted by Alembic

I have had some success with PbO2 Ti anodes. (Do a search for my old posts if you would like to see a picture). I have tried *many* substrates before that (carbon from batteries, pure graphite as well as ceramic) in the distant past but came to the conclusion that Ti is the most suitable.

BTW, the dimensions of the anode in the picture are 5cm x 30cm.

The process that I finally settled upon is a bit laborious but I have had pretty consistent results:

I used Ti sheet of about 1mm thickness because that is waht I had at the time. A little thicker would probably be better.



Next, a semiconducting coat of Sb doped SnO2 was applied by painting on a solution of SnCl4 + SbCl3 in water + butanol, drying, and then heating to 500 degrees Celsius or so in an oxidizing atmosphere i.e. air. This step was repeated five to ten times to give a suitable coating thickness. I will try to find the patent that describes this.

Then a thin (about 0.1mm) layer of alpha PbO2 was plated onto the substrate from a alkaline lead tartrate bath. See pat. GB 850,830 for info.

The final coat of beta PbO2 was then plated over top of this from a lead nitrate bath, also described in GG 850,830
This layer was about 2mm thick.

The anode performed well in a perchlorate cell.

-Alembic


Hello Alembic,

What grade of Ti did you use. Would it be a problem if pure Ti was not used.

Cheers,
Dann2
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hashashan
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[*] posted on 1-5-2007 at 22:45


actually i didnt. It was a one time setup.
I dont have any lead carbonate. however i thought that maybe the lead carbonate may be replaced with Copper carbonate as the copper also gets depleted. and i didnt think to coat anythin with Pt but just to use Pt and thats it.
also a nice ide i got was to combine the Pt with the cloth anode. I mean make a permanenet contact even befor the anode is ready bu clamping a
Pt wire and start to plate with it partially submerged, that way i dont have to take care of the solution too much right?
Here is the procedd i thought of:
rub in the paste into a cloth. insert the Pt piece ... clamp it. submerge the whole cloth and half of the Pt wire and start to plate at low curents untill we get a decent coating.

Another problem i had is that the second i submerged my rubbed in anode or even plastic with sprinkled PbO2 , all the PbO2 dissolved immediately, what can that be? too much acid in the tank? or any other reason?
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[*] posted on 2-5-2007 at 17:40


Quote:
Originally posted by hashashan
actually i didnt. It was a one time setup.
I dont have any lead carbonate. however i thought that maybe the lead carbonate may be replaced with Copper carbonate as the copper also gets depleted. and i didnt think to coat anythin with Pt but just to use Pt and thats it.
also a nice ide i got was to combine the Pt with the cloth anode. I mean make a permanenet contact even befor the anode is ready bu clamping a
Pt wire and start to plate with it partially submerged, that way i dont have to take care of the solution too much right?
Here is the procedd i thought of:
rub in the paste into a cloth. insert the Pt piece ... clamp it. submerge the whole cloth and half of the Pt wire and start to plate at low curents untill we get a decent coating.

Another problem i had is that the second i submerged my rubbed in anode or even plastic with sprinkled PbO2 , all the PbO2 dissolved immediately, what can that be? too much acid in the tank? or any other reason?


Only a littel Copper gets depleated because only a little gets deposited onto the Cathode. If there is a good blue colour there is probably enough Copper.
The Lead (or Lead ion to be more exact) gets depleated because it is being deposited on the Anode in the form of PbO2. As PbO2 gets deposited nitric acid forms in the solution. When you add Lead Carbonate (or Hydroxide, or Basic Carbonate or Litharge) it neutralizes the acid and increased the Lead Ion concentration.
I have noticed that if you try to plate with too low of a Lead ion concentration the PbO2 will be stripped from the Anode.

You could make a good connection to PbO2 with Platinum I would think IF the Pt is large enough to carry the current that your anode will be working with. A one mm diameter wire will not carry a very big current.

I read in alot of patents that the Lead Nitrate concentration should be at least 200 grams per liter. I have seen patents that use up to 800 grams per liter.

DANN2
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hashashan
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[*] posted on 3-5-2007 at 13:38


So any reasons i didnt manage to plate the anode?
the solution was pretty saturated, some crystals were even crystalizing out.
and why do you think that a short 1mm wire wont carry about 15 amps?
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[*] posted on 3-5-2007 at 17:12


Quote:
Originally posted by hashashan
So any reasons i didnt manage to plate the anode?
the solution was pretty saturated, some crystals were even crystalizing out.
and why do you think that a short 1mm wire wont carry about 15 amps?


Hello,

How much is pretty saturated?
How many grams of Lead Nitrate per liter were you using when you started to plated the anode.
Was the plating tank big enough so that the Lead Ion concentration did not get too low before the anode was finished plating.
Lead Nitrate solubility gets less and less as the Nitric acid concentration goes up and up. If you keep adding Lead Nitrate to the tank to replace the Lead Ions that have been used up, there will come a point where the Lead Nitrate will start to crystallize out on the anode. The Nitric acid concentration will be at a max. along the plating anode. You need to keep the Lead Ion replenished using a Lead compound that also neutralizes the acid.

1MM dia. Pt wire is thick enough to carry 15 amps. It would be near the absolute maximum I would ask it to carry. It may heat up too much.

Dann2
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hashashan
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[*] posted on 4-5-2007 at 02:47


the solution was neutral and some lead nitrate started to crystallize out, that why i say it was saturated.
the problem was that i mixed it with another solution that was pretty acidic (found out after the addition) it was about PH 1-2 maybe that was the reason that all the PbO2 that was sprinkled on the plastic and fabric was dissolved? or there might be another reason?
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