Before buying a kit to refinish the inside of my father’s CL100’s fuel tank, I thought it would be a good idea so see what would happen if the rust was removed. If there’s going to be any hope of re-using this tank, the rust has to go, and I need to know if there’s good metal underneath that oxidation.

I’ve heard of using electrolysis to remove rust a couple of times, but was always too nervous to try it out. Usually when I’m trying to remove rust I can get away with using wire wheels, brushes, sandpaper, etc... That’s not going to be an option this time.

The 2-gallon tank was completely dry, and has been for years. So I struck the tank a few times to shake free any loose rust. It’s already dented and scratched up on the outside, so I’m okay with that so long as I don’t introduce any new dents. So I rapped it on the workbench a little and shook out the contents. This is what came out:

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I stuck my scope down inside to see what was left. There was still plenty of very coarse rust at the bottom of the tank, much worse-looking than the thin layer that was visible at the top.

Scope view- LEFT: top of the inner hump. RIGHT: bottom of the tank.

I carefully removed the fuel valve (nearly destroying the retaining screw in the process), then decided that I was going to replace the whole assembly instead of trying to preserve or clean it. So I reattached it to keep the tank from leaking, and mixed up the solution: 1 tablespoon of sodium carbonate (washing soda) per gallon of water.

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I poured as much solution into the tank as I could and set the tank atop a drain pan just in case I find a leak. I fashioned a sacrificial anode out of some 1/4" steel rod that I had laying around, and forced it through a freshly-drilled hole in a scrap piece of wood. I then bent it to a shape that would not contact the inside wall of the tank and placed it into the fill hole.

A lot of modern battery chargers are too “smart” to be useful for this sort of thing, so I used an older-style manual 12V charger. I hooked the negative lead to the exterior tank mount, and the positive lead to the anode. After a quick test run at the 2 amp setting, I switched it to 10 amps and let it sit for a few hours.

I came back, turned it off, and cleaned off the anode. I then poured the nasty green-brown solution out, rinsed the tank, and put a fresh batch of solution in. I switched it back to the 2-amp setting for the night.

After 24 hours of pixie-dancing, the inside of the tank was starting to show some real progress:

Scope view- LEFT: top of the inner hump. RIGHT: bottom of the tank.

I dumped the tank and set it all up for another round. Not sure how many cycles this is going to take, but I like what I’m seeing so far.