Polyester resin (sold in car accessory shops, resin + hardener, it is a liquid and is NOT the same as 'car body filler') is very good for sealing around the anode, it 'wets' the Lead Dioxide and stops salts from creeping up the anode out of the cell. Hotmelt glue and silicon sealer have been used next to the anode but IMHO they are not as good as they will not actually 'wet' the Lead Dioxide but only sit against it and the salts will come creeping up along the inevitable gap the exists between them and the anode surface.
A piece of plastic is cut to a suitable shape for to place on the anode, a
washer shaped piece is needed for a circular shaped anode and a long piece with
a slit cut in it is needed for a filtration reinforced type anode. The hot melt
or silicon sealer (builders caulk) is placed underneath the plastic piece along
the anode and also in a ring around the anode on the top surface of the plastic,
as per the diagram. This is to stop the liquid resin from flowing away until it
sets. The resin is poured into the area around the anode where it flows into the
gap between the plastic piece and the anode and seals it. The anode, with the
plastic piece can now be placed into the hole in the lid of the cell and some
silicon sealer or hotmelt used to hold it there and seal between the
plastic piece attached to the anode and the lid.
It is advisable to use a separate piece of plastic to seal around the anode as per above because if you seal the anode into the lid directly it can be difficult to remove the lid together with cathodes and connections if you want to inspect the anode. It depends on your particular set up. The piece of plastic that is attached to the anode should be seen as part of the anode.
A word regarding copper contamination.
Copper is used in the plating bath and when using porous substrates (and perhaps non porous substrates) some of the plating solution will have penetrated into the substrate or may be incorporated in the electrodeposited Lead Dioxide. Copper is BAD news when dealing with chlorates/perchlorates, especially ammonium perchlorate. It would be advisable to be aware of this when using the first batch or so of product that your anode has made. It would be wise to not make Ammonium Perchlorate (from Sodium Perchlorate) for at least 2 runs of the anode so that all Copper will have leached away. A green colour has been observed on a newly made anode in a Chlorate cell, and it could have only come from the Copper in the plating tank.
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