Good video showing the practicalities of doing this. However, although this is being referred to as electrolysis, it isn't using the electrolysis to transfer rust to the anode in the way anodising works. What is actually happening is that the water is being separated into oxygen at the anode and hydrogen at the cathode. The oxygen is highly reactive with the metal anode and rusts it. However, at the cathode the hydrogen doesn't react but effectively blows the rust off the surface, sand blasting at atomic level. The result is that the rust on the rusty item ends up in the water, which is why it goes brown. There is no transfer of the rust to the anode. In fact, there ends up being more rust as there is now the rust on the anode and the rust from the item in the water. The anodes don't even need to be sacrificial for this to work, you can use stainless steel and it will still work, although some stainless steel will still rust under these conditions.

This also works as a paint stripper. I use this to remove the paint from metal items. They don't need to be iron, so long as they conduct.  It's best to lightly scratch the paint surface if possible but it works fine with old Dinky cars, etc. and works out much cheaper than using paint stripper, plus it's less toxic or harmful, both to yourself and the environment.

I also have an easy way of remembering which way to connect: +ve to "adding rust"   -ve to "subtracting rust".

I set up the same type of cleaning unit a few years ago. A friend had a large box of assorted tools under his work bench in his garage and his wife opened the window to "air" the garage out and left it open. There was a torrential downpour and his box was filled with water. A year later he pulled the box out to sort out his tools for a garage sale and found them rusted together into a large mass. He classed them as useless and asked me if I wanted them. 2 weeks later I'd run all the tools and many drill bits through my electrolysis bath and I'm now the proud owner of a complete collection of rust free hand tools. All with a beautiful black sheen. I even discovered two American shifters made in 1906, now fully working.

The only downside of the routine was the mess following heavy use of the bath. It leaves a very nasty looking scum on the surface which stains anything it touches. I wouldn't advise putting this down the drain, probably best to dispose of somewhere in the garden. You can get a slight tingle if you dip your bare hands in the solution, but it's not enough to cause discomfort. Don't forget, some chargers use 24 volts and 12 volts, I advise 12 volts for safety reasons. After the de-rusting and cleaning your tools, I give them a light spray of thin oil (WD-40 is OK) and a wipe with a rag, this will protect the tools from rusting again. One final tip, never cover the bath during use, hydrogen is produced (the fizz) and with those electrical connections a spark may cause it to go boom. Oh yes, any chromed tools will lose their shine, but don't worry. the resulting black sheen looks even better. :-)

There are two types of rust.  The first step of the rusting process produces Magnetite (Fe304), which is tightly adherent to the iron and is black in color.  If you leave it longer, you get red rust (Fe2O3), or hematite.  Red rust takes up more space than the iron it replaces, so it flakes off.  

The electrolysis process causes the red rust to detach from the underlying metal because of the bubbling.  The black rust that underlies it actually is reduced back to metallic iron by the current.  The density of the resultant iron is maximized by using a low voltage 2-3 volts over a long period of time, but the 12V method also works pretty well.

Nice technique. But the fizzing… that’s hydrogen- and oxygen-gas  from splitting the water molecules. Make sure you ventilate! Leaving it “for a couple of hours” in a closed space can build up something you do not want.

I've used electrolysis many times.  Dom's vid is good.  I've often done a pile of things. Don't even have to connect wires directly to all the parts, as long as they are touching each other, it works. (better of course to connect wires). Also, as to only a few hours, depends on how rusty the items are.  I've occasionally needed to leave the product in for a week.  No big deal.  Does a stunning job.  NO elbow grease required.  Leaves the finished product sort of "black".  Why?  Cause the hard to remove red rust, (ferrous oxide) is replaced with ferric oxide, (black rust). Black Ferric oxide is fairly easily washed off, leaving a clean surface.  
sometimes you have a BIG item.  Easy to build a wooden frame, lined with plywood, then line that with polyethylene sheeting.  You can put in a large free standing machine that way.  As Dom said, don't use a fancy charge controller.  Some of those don't recognize what you are trying to do, and don't "see" a battery, so won't work.  You can trick those by putting a battery inline too, so that it thinks there is a battery that needs charging though.

should be noted that the fizzing is generating some tiny amound of hydrogen, which isnt that big of a deal in a good sized shop space

I would warn against using just any kind of steel for the sacrificial anode(s). If you use a Stainless or relatively high Chromium content steel, it will make your leftover water very poisonous. Not something you should then pour down the drain! So, only use mild steel and similar for your anodes.

In an age that seems to be losing the ability to "make good" otherwise usable tools, it is refreshing to see the art is still alive and kicking.
Thank you Sir .

You can also do this inside-out.  I used this method to remove the rust from the inside of a motorcycle gas tank. Negative to the bare metal of the tank, positive to a large bolt suspended inside the tank full of sodium carbonate solution.

I'm from the USA and at 70yrs cant tell you how much I appreciate this video. Although most of my tools are kept spotless, I, like you go to swap meets and garage sales and have picked up some great older tools and this will help restore them. Keep up the great work.

I discovered this a couple months ago and already saved hundred in tools. I’m about to clean out my garage and I can’t imagine how many tools I would’ve thrown out if I didn’t come across this method. The best results is soak 24 hours, scrub with wire brush, soak for another 24 hours, light scrub with wire brush then rinse dry and oil to prevent further rust.

Hi Dom, I think it would be worth mentioning that during this type of electrolysis, the electrolyte will release hydrogen gases...this could be dangerous in a confined environment...so a well ventilated room is indeed necessary...

Best tutorial for electrolysis on YouTube. Explained very well.

Great video, the thing about old tools is that generally they are far better than the new tools for sale out there today.

I have been faithfully watching your endeavours in the REPAIR SHOP and today I stumbled on your YouTube site. From now on I shall double the pleasure of watching the wonders you make. I hope you don't stop showing us what you make.

Brilliant video. Recently started blacksmithing and bought some old tools to get up and running and this looks like the ultimate way to restore them to their former condition. Thanks to all who have highlighted dangers from poor ventilation. I would add the importance of switching off power BEFORE disconnecting any components as even a small spark could ignite that oxy/hydrogen mix. The process is similar to charging a car battery and I have had to give first aid to someone who removed lead with power on and the spark blew up the  battery. (almost blinded him) Careful !!!

I have been using electrolysis for a number of years. It is a permanent part of the tool restoration business here at Old Sneelock's Workshop.
I use to be in charge of repairs in an aluminum anodizing shop. I replaced the expensive stainless steel tanks with plastic lined steel.
When I retired and started restoring tools I used large wooden boxes lined with plastic sheeting for electrolysis. You can put very large pieces in a wooden crate and it is inexpensive to make any size you need.

Someone not scared to show practical stuff - well done Dom!

If electrolysis managed to remove my ex’s tashe , rust should be no problem. 😂

Great video Dom. Hope your workshop is a great success.