Electrolytic Reduction Process


by Bob "Frogfoot" Weller


  If you can use an all-glass tank (aquarium) for your electrolytic reduction tank, it will help you ”see’’ what progress you are making in the preservation process. If glass is not available. You can use a five-gallon plastic bucket if you have to. The electrolyte solution depends upon the size of your container and the amount of distilled (if available) water you put in the tank. Remember, the electrolyte solution merely transmits the electrical energy that causes the reduction of sul­fide. You can use vinegar, baking soda. or Red Devil bathroom lye (any food store) as your electrolyte. I use about a half-cup of lye or baking soda to three gallons of water, and this seems to do the trick.

Clip-on leads can be purchased from any Radio Shack or similar store. Use these to clip the coins to the holding bar (cathode) across the top of the tank. The holding bar can be a stainless steel rod 1/4” diameter, or any supporting rod that will conduct electrical current to the clip on leads and coins If I have to use a plastic bucket to run the reaction, I drill a couple of holes, one on each side of the bucket, and run my holding rod through these to hold it in place. Otherwise, the rod wants to slip off or move around.

The anode can he anything of 303-304 stainless steel, a plate, a rod, even a large, heavy-duty bolt. The surface that the electrolytic reduction has to work with determines the rate at which the reduction takes place. If I use a large plate, and I do not want the reduction to go last (it may mar the surface of the coin….you can see it bubbling too fast), I cover part of the stainless-steel bar with Vaseline©, which reduces the surface of reaction. Never shut off the battery charger while the coins are still in solution, the reaction will reverse itself and you’ve got a mess on your hands.

Clip the RED (+) lead of tile battery charger directly to the an­ode and the BLACK (-) lead directly to the rod (cathode) holding the clip-on coins. Put the charger on six volts at first to see how fast the reaction takes place. If nothing is happening within several minutes, the connection may not he too good, or the battery charger may have a timer (minutes/hours that is set on zero) and will require your setting up a time on the battery charger to energize the system. If the coins do not seem to be percolating, check the clip leads on the coins, make sure they are well clipped to the holding rod.

The coins, if only blackened, should he completed in a matter of a Few minutes. If they are heavily sulfided it may take as much as one hour at six volts, or thirty minutes at twelve volts. The black Sulfide will drop off the coins, and this will give you an indication that the reaction is taking place.


Some words of caution!!


You're dealing with household electricity, so an electrical shock is always a danger. DO NOT come in contact with both the anode and cathode at the same time. It makes your hair curl! The electrolyte can cause some skin damage, so always wash thoroughly when you are finished. Wash the coins thoroughly as well. From time to time (I2 hours) check the stainless steel plate you are using as an anode. You may have a build-up of residue that will have to he scraped off to continue with the reduction.

You can use this system to preserve iron objects in the same manner that you have used for coins. It just takes a bit longer because the salt has really gotten into the iron.






This excerpt was taken from Salvaging Spanish Sunken Treasure

by Bob "Frogfoot" Weller

with permission.


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