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How to remove rust with Electrolysis
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Author:  earlymb [ Mon May 16, 2016 12:22 pm ]
Post subject:  How to remove rust with Electrolysis

Electrolysis has been mentioned in a number of topics in the past but I believe there hasn't yet been a special topic dedicated to this subject.

Electrolysis is a method to remove rust from metal objects submerged in a solution by using an electric current to start a chemical reaction. It is the least invasive method to clean metal compared to sanding, wirebrushing, nasty chemicals or other invasive methods. It's also clean, safe, very cheap and will leave the patina intact. It is however not suited to stabilize rust, so objects that more or less completely turned to rust (like ground dug helmets) will dissolve with this method. Also, it will remove paint.

IMPORTANT: this process will generate hydrogen, so only do this in well-ventilated areas, preferrably outside and keep anything that can ignite it away!

I will illustrate the process with a 1943 dated machete I recently aquired from a junkshop. A nice solid example that had lots of surface rust, a few spots were the rust started to actually pit the metal and some remains of green paint. As such I thought it would be a great candidate to give electrolysis a try (sorry, the before-pics are not the best quality).

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The supplies:

You'll need the following supplies:

- A plastic or glass (anything non-conductive) container, large enough to be able to submerge the object you want to clean;
- Some sacrificial scrap metal to use as an anode (rebar, old brake drums, cast iron grilles etc. is perfect. No aluminium, stainless steel, copper etc though!);
- A standard 6, 12 or 24V car battery charger;
- Standard cleaning/household (NOT baking!) soda.

The process:

- Fill the container with room temperature tap water, enough to submerge the object you want to clean.
- Add the cleaning soda (about 1 tablespoon per 4-5 litres) and stir well to dissolve it.
- Put the sacrificial piece of scrap metal in the container and connect it to the positive (+) clamp of the battery charger. IMPORTANT: this piece of scrap metal and anything connected to it will dissolve over time. Therefore, make sure that the positive lead is connected in such a way it does NOT make contact with the water/soda solution. Nothing will happen with this clamp & cable as long as it stays dry.
- Put the object you want to clean into the solution and make sure it is submerged. If too big for the container it can be done in sections though. Connect the object to the negative (-) lead of the battery charger. This clamp can be submerged in the solution, nothing will happen to it.
- Make sure the object and the sacrificial scrap metal don't make contact directly, or you'll have a short circuit!
- Switch the battery charger on & give it time. This process will not touch the original metal so it can stay overnight if needed. Usually it will take a few hours at least. As soon as you switch it on you'll see tiny bubbles start rise from the object you want to clean.

Again, this process generates hydrogen so make sure the area is well-ventilated and clear of anything that can ignite it!

This is the set-up I used. The piece of rebar goes all the way to the bottom of the container and I used some ducttape to secure it to the side of the container. You can also use a clamp or a U-bolt to secure it. Although I used only one anode here, more anodes will make the process go quicker. If you want to use more anodes, just connect them all with some standard electrical wire. Make sure both the clamp of the battery carger and any electrical wire stays away from the solution! As you can see, the positive clamp is attached well above the solution.

I used the thong of the machete to tie it to handle of the container to secure it and make sure it won't make direct contact with the anode. Then I put the negative clamp of the battery charger on the machete, this one can make contact with the solution and nothing will happen to it.

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I took this photo about 2 hours after I put the charger on. The brown stuff is actually dissolved rust from the machete, and there is also some green paint that came off. This is a 12V, 10amp charger but 6V & 24V and anything above 2amp will do. You can scoop the crud off the surface if you want, but stirring the solution once the electricity is on will only slow the process down.

This is the result after about 5 hours in the solution. After taking the machete out I rinsed it with fresh water, dried it and finished with a bit of steel wool.

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The solution is completely free of chemicals, so when you're done you can use it to water your garden without problems. The dissolved rust and soda even make good plant nutrients. Ofcourse you can also just poor it in the drain, but beware for stains the dissolved rust might cause if leaked. The piece(s) of sacrificial scrap metal will slowly dissolve over time, but till then you can just clean them with a wirebrush and use over & over again. In theory you can use this method to clean metal objects of any shape & size. Some even cleaned trailer frames in swimming pool-sized containers with a suitable power supply...

I already had the battery charger, piece of rebar and container, so I guess this process cost me about €0.25 in soda and electricity.

There is a lot of additional information on this subject on the internet. I hope this guide will help someone too! :D

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