Home produced Magnetite anode using welder and annealing oven

The following anode when used in a K Chlorate cell at a current density of 63mA per square cm showed a very poor current efficiency of approx. 12%. Perhaps with lower current density this might improve. pH control would probably help. 11 Volts was needed to drive current into cell. The Silver metal connection on Magnetite seems to be high resistance. Copper may be better.

The anode is produced by 'welding' (melting using the welder) ceramic grade (from ceramics store) Magnetite powder in a heated mold.
The still red hot anode and mold is placed into an annealing oven where is is cooled to room temperature over a period of about 36 hours.

Below is the simply mould, 'kiln' and annealing oven.
The Magnetite is melted in the mold using a welder with a gouging rod as an electrode. A piece if steel is temporarily welded to the mold to allow the earth attachment.
As the Magnetite powder is being melted in the mold a propane torch is left burning against the mold in the kiln to keep the temperature up. The mold should be cherry red hot. The anode has to be turned over to facilitate the melting of the second side. It may have to be turned over again to melt the first side again in order to tidy it up.

The mold should be made so that the sides can be easily moved. This allows you to turn the anode. It consists of two pieces of L shaped square section steel as per the picture sitting on a flat piece of steel. Using heave steel is recommended to give the mold large thermal inertia (won't cool down quick). This is necessary as when you are transferring the anode + mold to annealing oven it cools rapidly which is something you do not want happening. Use two pieces of L shaped heavy steel wires to transfer (quickly) the mold + anode into the annealing oven.

The annealing oven consists of a (biscuit) tin box containing two domestic electric heater elements. They can be obtained from discarded electric fires or purchased new. The elements are surrounded by volcanic rock called Perlite. This is purchased in a garden shop and is used for mixing with clay to make it more workable. Asbestos roofing slates or 'fiber board' for stoves is used to make a chamber around the heating elements.
Two pieces of box Iron cut approx. 2 inches long and a part of their wall removed are used are used as the stands to put the mold + anode sitting on above the heating elements. The mold must not touch the heating elements. A lid is needed for the oven. Some fiber board or slate + Perlite will suffice.

The power going to the elements was controlled using a variac. You could probably use a large resistor made from another heating element, tapping it in the appropriate place. Careful of electric shock.

Test the oven before you start to see what wattage is needed to give you a starting heat of about 800 Centigrade. The oven must be red/orange hot when mold + anode is put into it.

It is beneficial to melt the Magnetite powder outside the kiln on a piece to Iron plate in order to make Magnetite nodules. They are easier to work with when you start to make the anode proper in the kiln.

Pictures below show 'kiln' with mold and propane torch
Annealing oven
Anode approx. 19cm long

[picture of mold and 'kiln'] [picture of mold] [picture of annealing oven] [picture of anode]

[picture of colour of temperatures]
This image shown colour in relation to temperature in Centigrade