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Author: Subject: Copper substrate lead dioxide anode
Bogdonovan
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[*] posted on 12-11-2019 at 00:17
Copper substrate lead dioxide anode


Is it possible to do something like this? Is there a better alternative? I plan to melt lead from old wheel weights and dip some 5mm copper sheet in lead multiple times to make a thick coating, then electrolyze to it to lead dioxide in solution of 30% sulfuric acid. Im making these to use in a chlorate cell. Any input is appreciated.
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phlogiston
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[*] posted on 12-11-2019 at 02:32


I can see two potential problems.

1. If the lead dioxide layer has even so much as one tiny pinhole, the electrolyte will access the substrate and destroy it.
This is why substrates are preferred that are resistant to the corrosive effect of the electrolyte. (eg Graphite, ceramic, titatanium, platinum, etc.)

2. Even if the lead dioxide coating is perfect, contact between the lead dioxide and copper will oxidize the copper, forming a non-conductive interface between them. This is why a layer of silver is often used in between copper and lead dioxide coatings (silver oxide being conductive). Maybe buy one of those bottles of silver-based conductive ink? They are sold for manually painting/reparing tracks on circuit boards.

[Edited on 12-11-2019 by phlogiston]




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rockyit98
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[*] posted on 12-11-2019 at 06:46


Quote: Originally posted by phlogiston  
I can see two potential problems.

1. If the lead dioxide layer has even so much as one tiny pinhole, the electrolyte will access the substrate and destroy it.
This is why substrates are preferred that are resistant to the corrosive effect of the electrolyte. (eg Graphite, ceramic, titatanium, platinum, etc.)

2. Even if the lead dioxide coating is perfect, contact between the lead dioxide and copper will oxidize the copper, forming a non-conductive interface between them. This is why a layer of silver is often used in between copper and lead dioxide coatings (silver oxide being conductive). Maybe buy one of those bottles of silver-based conductive ink? They are sold for manually painting/reparing tracks on circuit boards.

Copper - lead dioxide contact supposedly does not work well, because the lead dioxide can oxidise

it can work because PbO2 isn't in contact with copper, only with raw lead.but PbO2 with Pb can flak off.mainly because PbO2 and Pb have Thermal expansion gap.




i guess it's time to change the signature.
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phlogiston
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[*] posted on 12-11-2019 at 15:38


Sure, but then it is going to be tricky to convert just enough of the lead layer to PbO2 to leave a little bit of lead metal to protect the Cu-PbO2 interface.



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Bogdonovan
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[*] posted on 12-11-2019 at 23:59


Quote: Originally posted by phlogiston  
I can see two potential problems.

1. If the lead dioxide layer has even so much as one tiny pinhole, the electrolyte will access the substrate and destroy it.
This is why substrates are preferred that are resistant to the corrosive effect of the electrolyte. (eg Graphite, ceramic, titatanium, platinum, etc.)

2. Even if the lead dioxide coating is perfect, contact between the lead dioxide and copper will oxidize the copper, forming a non-conductive interface between them. This is why a layer of silver is often used in between copper and lead dioxide coatings (silver oxide being conductive). Maybe buy one of those bottles of silver-based conductive ink? They are sold for manually painting/reparing tracks on circuit boards.

[Edited on 12-11-2019 by phlogiston]


I thought about something like this, my suspicions are confirmed. I can try make some of what i call "part graphite" by blasting a ton of air into a charcoal fire and extinguishing it a little after, picking out pieces with low resistance, then making a paste from them. Its conductive enough to work for this, i think. Is it a better idea to then use copper coated with the carbon coated with the lead dioxide or to just make a big rod of the graphite stuff and coat that? Will have to experiment. Thank you and rockyit98 for the info
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phlogiston
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[*] posted on 13-11-2019 at 06:41


Wow, that seems an unnecessarily primitive method to obtain something resembling graphite. If using absolutely zero commercial materials is a boundary condition for your project, that adds tremendously to the difficulty of making an lead dioxide anode.

I now remember you also started a thread on making sulfuric acid with a near-0 budget, and also for that project a source of graphite electrodes would be helpful for you.

If you are doing it for the fun of a challenge, I can appreciate that. Otherwise, I think that maybe it would be a good idea to focus your efforts on obtaining graphite first, and then returning to these projects later. Graphite should be available in most parts of the world at very little cost. At the very least, you should be able to obtain a pencil. Crushed-up pencil is already a lot better than whatever you can make in your foundry.

You can also harvest pretty good graphite rods from discarded batteries. A bit small, but good quality graphite. Definitely useable.

You could also try making a non-conductive substrate conductive (eg ceramic) by coating it with graphite powder or even by drawing on it with a pencil. This method is commonly used to make all kinds of objects conductive for electroplating.

[Edited on 13-11-2019 by phlogiston]




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Bogdonovan
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[*] posted on 14-11-2019 at 02:57


Quote: Originally posted by phlogiston  
Wow, that seems an unnecessarily primitive method to obtain something resembling graphite. If using absolutely zero commercial materials is a boundary condition for your project, that adds tremendously to the difficulty of making an lead dioxide anode.

I now remember you also started a thread on making sulfuric acid with a near-0 budget, and also for that project a source of graphite electrodes would be helpful for you.

If you are doing it for the fun of a challenge, I can appreciate that. Otherwise, I think that maybe it would be a good idea to focus your efforts on obtaining graphite first, and then returning to these projects later. Graphite should be available in most parts of the world at very little cost. At the very least, you should be able to obtain a pencil. Crushed-up pencil is already a lot better than whatever you can make in your foundry.

You can also harvest pretty good graphite rods from discarded batteries. A bit small, but good quality graphite. Definitely useable.

You could also try making a non-conductive substrate conductive (eg ceramic) by coating it with graphite powder or even by drawing on it with a pencil. This method is commonly used to make all kinds of objects conductive for electroplating.

[Edited on 13-11-2019 by phlogiston]


Unnecessary primitivity is my shtick. I do use commercial products that i can find here and are cheap, this narrows the list down a ton. Ive settled on making the sulfuric acid from hydrogen peroxide and sulfur. Im mostly doing this for fun, but id also like to get a result at the end. Graphite is obtainable but i always try to go the max cheapo route. Ill have to test the charcoal stuff to know if it works, if it does i dont think i need anything better. The coating non conductive things is interesting but i dont think it will come in use in my situation.
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