THE MINI MAG. Volume 2 No.10
  October 2000

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Home Restoration.
 Rust removal from small parts.

Electrolytic rust removal is a novel method of removing rust from small mechanical parts, and apparently also removes grease, dirt and sometimes paint, with little effort. The advantage over traditional acid dipping, wire brushing or sandblasting is that the rust is converted back into iron instead of being removed from the piece. For this reason this method is often used by restorers of antique tools and other iron artefacts. For some reason this method seems not to be very well-known among car restorers.

Note: I have not yet tried the methods described on this page. The instructions are compiled from a number of sources. Also, this process works only on iron parts (not aluminium).

Items Needed
 Washing soda (available at supermarkets).

 A container large enough for the parts you will be cleaning. It must be plastic or some other non-conductive material.

 A car battery trickle-charger (capable of delivering at least 5 amps and preferably with an inbuilt current meter).

 Electrodes - any piece of iron, e.g. a piece of old angle-iron. Make it large enough to protrude from the container so a jumper-lead can be connected to it.

 Jumper-leads or cable rated for 5A (mains flex would be fine).

 Water

Method
1. Mix water and washing soda in the container. The ratio is approximately 20 litres of water to 1/2 cup of washing soda, or a tablespoon per 4 litres. Mix until the washing soda is dissolved.

2. Place electrode into container. Clean it if it is rusty so good electrical contact can be made. THE ELECTRODE MUST NEVER BE ALLOWED TO TOUCH THE PART BEING CLEANED. Several electrodes can be used, provided they are connected together.

3. Suspend the part to be cleaned in the container so it does not touch the electrodes or the bottom of the tank. (e.g. tie a piece of string to it and a piece of rod over the container).

4. Attach the battery charger NEGATIVE terminal to the part that is to be cleaned. If you used wire or chain to suspend the part, you can connect the wire to the chain above the solution, for convenience. If you connect the terminals backwards, your mechanical part will be eaten away.

5. Attach the battery charger POSITIVE terminal to the electrodes.

6. Double-check that the part and the electrodes are not touching.

7. Turn on the charger and check that current is flowing. Wait several hours, check progress at intervals. It may help to clean the part occasionally to encourage the rust-converting action - you may see the current decrease when this is necessary. Bubbles of hydrogen and oxygen will rise from the piece.

Additional Notes
 It may be necessary to remove loose rust scale first, by lightly sanding/scouring.

 Forming the electrodes to the approximate shape of the part may increase the efficiency of the process, as might suspending an electrode inside a part that has a cavity or is hollow - the action is almost "line of sight" so several electrodes or rotating the part may be necessary.

 The electrodes will eventually wear down and require replacement.

 THE PART BEING CLEANED AND THE ELECTRODE MUST NEVER TOUCH. This will short-circuit the battery charger. A good safety measure would be to fit a fuse in-line with one of the terminals, of double the normal charging capacity of the battery charger.

 Don't try and use a car battery in place of the charger, as it's the current flow rather than the voltage that is important. A car battery will short-circuit and may explode or be destroyed in this circuit.

 Use adequate ventilation or do the process outside, since it produces highly explosive hydrogen and pure oxygen gas.

 The process can be scaled up to any size that you can manage - doors, bonnets and boot lids could become candidates for this process.

 The waste water is safe to dispose of in a household drain, as long as the original part was fairly clean, and the electrode was not galvanised iron and there were no funny looking chemical reactions in the solution

 The process may leave a residue that can be cleaned off using a fine grade Scotch brite pad.

 Spray the cleaned part with WD40 or paint it or it will start to rust after a very short time.

 Some types of stainless steel will not degrade when used as an electrode and therefore last much longer than iron.

 If the surface was damaged or pitted by rust, this damage will not be reversed.