Rust Removal by Electrolysis

Electrolytic Rust Removal

I was looking for a way to remove rust from old motorcycle parts, so I started searching. The main methods that I already knew about were acid baths and mechanical removal, such as sanding or sand blasting. These methods can be effective, but they both have troubling side effects. There are some other chemical baths, but they are pretty expensive.

I liked the electrolysis method for several reasons. One is that it doesn't remove good metal, and the other is that the bath doesn't pose an environmental hazard.

The first requirement for electrolysis is electricity. Some people use a battery charger, but since I didn't have one handy, I decided to use a computer power supply. The power supply already has short circuit protection and several other nice features, and in my case I always have a few old computers lying around. I've used another computer power supply for making a 12-volt SAE (cigarette lighter) jack so that I could run car intended accessories away from the car. If you are interested in converting a power supply and you know how to solder, you should get some inspiration from the picture below. Depending on the power supply, you may have to do some head scratching to get it to turn on, since most modern computers have a switch somewhere on the front of the chassis. I had to add a switch and short some wires on the supply in the picture. I won't explain it here, but you should be able to figure it out with an hour of google time or less. If you aren't confident with soldering and using a multimeter, or if you are intimidated by the label that says "do not open," then just procure a car battery charger instead.

The second important ingredient for electrolysis is water. After all, that's really what the idea of electrolysis is all about- turning water back into hydrogen and oxygen. That's also an important reminder that the process produces explosive gasses, though in very small quantities. Since pure water isn't a very good conductor of electricity, I added sodium carbonate. This is sold in some grocery stores as washing powder. My regular grocery store didn't carry any, so I had to go to Harris Teeter. The $3 box will probably last a lifetime at 1 tablespoon per gallon.

My next step was to put the positive lead on a piece of sacrificial steel, then to put the negative lead on the part. Some people have said online that they use stainless steel so that it doesn't dissolve during the process. In truth, it does dissolve, just at a slower rate than plain steel. The trouble is that when it does dissolve, it leaves traces of chromium in the water, which has serious negative environmental implications. I recommend just using plain steel pieces that you are willing to lose. If you haven't already realized it yet, there is scrap steel all around you. For instance, I used a bent clutch pushrod and a broken gear shift lever with great success. It is very important to suspend the wire and aligator clips so that they are not submerged. You want the rebar or other sacrificial metal to be the only positive lead in the water. Otherwise, your copper wire will readily dissolve and disrupt the connection. If you see green floaties, then you know you've messed up.

Here is my test run in a cool whip tub.

With my small-scale proof of concept a success, I started on the big tub. To get the solution correct I used a 5-gallon bucket and a 5 tablespoons of powder. I repeated that process until I had enough to submerge the parts, since the exact mixture isn't really too critical. The solution is reusable, with the exception of that the water level slowly sinks due to evaporation and electrolysis. This level change is really not something you can notice without some careful tracking. If you do notice a drop in the water level, just add plain water to bring it back up. The washing powder doesn't go away, just the plain water.

The shovel turned out to be a poor electrode, simply because I didn't clean the rust off. Even if you start with a clean electrode, you will find that it gets rusty during the process. After a day or so you may have to take out the electrode and clean it up with a wire brush. Below you can see an "after" version of the skid plate and a before and immediately after with the battery box. Even after treatment, the parts still need some minor wire brushing to finish the job.

Just be sure to clean the parts with something like denatured alcohol and then paint right after treatment so that they don't rust again. They'll re-rust in a matter of hours in the southeastern US.

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This page last modified 06/10/24