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This (probably) is the first web-published attempt to make a lead dioxide (PbO₂) anode using a plastic substrate. I published a set of pictures on year 2000 without comments, so some of you may already saw them. There are other my plastic anode pictures in Micheal Mc Ardle site of the very first attempt I made (1999?).

Background

There is a little and virtual community around the world that is playing with lead dioxide anode. These anodes are hard to make but are a way to put on work an electrolitic cell to produce sodium perchlorate. One can use an expensive platinum anode too, but it's not funny! Lead dioxide anodes are made of an inhert substrate (graphite, ceramic, plastic, ...) and a thick layer of beta lead dioxide. Plating over graphite is relatively easy, because graphite is conductive. Ceramic and plastic have to be made conductive with some kind of treatment. This is what I'm starting to describe for a plastic substrate. I've done the same for a ceramic substrate (seek csld on menu).

Why plastic?

Plastic is ready available in many shapes. Giving a particular shape to a piace of ceramics (carborundum) is a task I wouldn't take. Graphite is harder to find, and it, even if inhert, presents wear problem.

Make the plastic conductive

Not easy. I use a piece of polystyrene (PS) plastic which is soluble in trichloroethane. I think many plastic materials are soluble in trichloroethane. Just chose a potential substrate and try. I always use piece of plastic box discarded after the content is well confined in my stomach (normally chocolates) :-). A floppy disk can be useful (my first attempt...) but it is too weak. You can use it to do some exercice.

Acetone is another possible solvent, try with it and make me know!

The treatment consists in "glueing" a layer of powdered lead dioxide on the substrate. I make a "paste" with lead dioxide and trichloroethane. Then I paint the plastic with this "paste" using a little brush. The trichloroethane quick dissolve a thin layer in the plastic substrate and quick evaporate, leaving the PbO₂ fixed.

With this procedure you won't get an hyper conductive piece of plastic, but enough to plate it.

Contact

The contact between the anode and the power supply wire is made with a piece of goungin rod worked to an adeguate shape. It is glued to the plastic and the electric contact is made putting some lead dioxide on the edges.

To protect the metallic part of the contact I used some polystyrene dissolved in trichloroethane. Please, use and acrylic color instead. I use "Veronose green" (Maxcryl series, Ferraio - Italy). It worked great!

Plating

Deposition of lead dioxide starts near the contact and extends through the substrate slowly. So there is a more thick layer of lead dioxide over the contact, but it is a good thing: this point carries an high density of current while working in the perchlorate cell. Still, when all the substrate is covered with a minimum of plated lead dioxide, the plating process continues uniformly.

Does it work?

Partially. The substrate I used was too weak and bended while plating. Not a good thing! I plated a thin layer, too, so it destroyed in few days into a perchlorate cell (but driving some amperes). Potentially it is a good anode. May be problems raise if the cell get too hot.

References

Michael McA. site

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