How To Clean Coins with Electrolysis - A Detailed Illustrated Tutorial, page 18
Process of Coin Electrolysis
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5) How To Control Voltage & Current During Electrolysis
Controlling voltage and current during electrolysis is essential for achieving good results without wasting energy through excessive heat at the wire connections, or overheating the power supply. Controlling voltage and current also ensures that your electrolytic setup remains effective throughout the process, i.e. it does not take more time than necessary to clean the coin.
If you use an AC/DC adapter for your electrolysis devise, you really can not get more voltage/current out of it than what the adapter is specified for because it does not have any voltage or amperage controls. With such a power supply, you can either maintain the voltage/current inside the electrolytic cell on the highest possible level or reduce it by positioning the coin further away from the anode, or using the weaker electrolyte. If the adapter's output is not sufficient enough, replace the adapter with one that has higher amperage (above 700-800mA).
However, if you need to mechanically work on the coins between sessions, you better use the low voltage power supply - a 6V adapter, for it works slower but does a good job. If you take it slow, you can stop the process before you get to the coin's bare metal. Also a mixture of sodium carbonate and sodium bicarbonate in the electrolyte increases efficiency of your setup.
If you use a car battery charger, you can easily control the voltage/current inside the electrolytic cell, which allows for better control of the process. The higher the voltage, the higher the current, the quicker the coin cleaning process.
Increasing the current will certainly ensure faster cleaning; however, amperage, just like voltage, must be kept below dangerous levels in order to protect the electrical wires, connections and the power supply from overheating or short-circuiting. When the current flow is far too high, excessive anode erosion will also occur. So when the current is reaching a dangerous level, one must act quickly to reduce it back to acceptable levels.
Using an ammeter built into the car battery charger is the best means to control the current because the ammeter gives a useful indication of the actual current flowing. But if your power supply does not feature an ammeter, you can determine when the current level is too high by the electrolyte's hot temperature.
• If the Ammeter is not available, there are four ways to reduce the current:
1) by increasing the distance between the anode and the cathode (coin). Turn off the power source before moving and securing the electrodes at new positions to avoid the electrodes' accidental touching one another - short-circuiting.
2) by reducing the amount of submerged surface area of the anode by elevating it out of the electrolyte a little - this takes less time than increasing space between the electrodes, and the anode must be firmly secured after each move.
3) by reducing the voltage (which would also reduce the power consumption) - this seems to be much easier if your car battery charger has a 12v/24v switch, and you just switch the voltage from 24 to 12 volts.
4) by diluting the electrolyte with distilled water - this will take longer than repositioning of the electrodes because it would be hard to determine the optimal concentration of the electrolytic solution even after a few attempts.
Obviously, to INCREASE the current passing through the electrolytic setup, one has to do the opposite to the means described above. In any case, these current-controlling techniques are not as practical as a simple turning of the ammeter's amperage knob, especially when you have to clean many coins. You may want to read more about Using Ammeter & Checking Its Readings on page 23 of my "Removing Rust from Iron Relics with Electrolysis" Tutorial.
• What is hydrogen embrittlement?
The electrolytic reaction supplies electrons to hydrogen ions in the electrolyte, changing them into hydrogen gas: the more current, the more hydrogen. When the applied current is too high, the smallest hydrogen atoms from the electrolyte can be forcefully interposed between the base metal molecules on the surface of the coin being cleaned. This can affect the surface to the point of micro-cracking that may be visible only under a microscope. It is more likely to happen when the current is set on a highest level possible to achieve rapid de-crusting.
• Wasting Energy Through Heat
The heat is usually caused by electrical resistance of the wires that are too thin - their gauge is not proper for the voltage setting. Heat does not add anything to the process, other than wasting electricity.
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