Electrolytic Rust Removal From a Motorcycle Gas Tank




Introduction: Electrolytic Rust Removal From a Motorcycle Gas Tank

The following is the process I used to remove rust from the inside of a motorcycle gas tank.

All the information herein can be (and was) found on the internets. This was my first foray into electrolysis and I supplemented my newly gleaned knowledge w/ much caution.

Keep an eye on our fledgling blog, dorque.net, for more Honda CB related goodness.

Step 1: Materials & Tools

What you need:
 - A gas tank with rusty innards
 - Some Arm & Hammer Super Washing Soda
 - A sacrificial anode made of steel (but not stainless) or iron
 - A battery charger
 - Some scrap wood
 - A bucket
 - Water

Step 2: The Sacrificial Anode

The sacrificial anode must not come into contact with the gas tank.

The anode itself is a piece of steel rod formerly used to hold up a plant (I think). Stainless steel will produce toxic substances during this process, so steer clear of it.

To suspend it inside the tank I fashioned a collar of sorts out of some scrap wood. The rod is bent above the collar to keep it from sliding into the tank and bent below to thread the narrow clearance between the underside of the top of the tank and top of the bottom ridge.

Note the amount of rod above the collar. This is a mistake. The extra weight actually pulled the bottom part of the rod into contact with the top of the tank when the battery charger was later connected.

Step 3: The Electrolytic Solution

Fill up the bucket with enough water to fill the gas tank.

For every gallon, add a tablespoon of of the Arm & Hammer Super Washing Soda. Adding more doesn't speed up the process, but I haven't read anything to suggest more soda will impede it either.

Stir thoroughly.

When all the soda is dissolved, top off the tank with the solution.  Be sure to put a cork in any holes in the bottom of the tank (for petcock etc.)

Step 4: Hook It All Up

Attach the negative lead from the battery charger to the tank.
Attach the positive lead to your sacrificial anode.

Turn on the charger. I dialed mine to the 10amp setting. Leaving the charger on at the 50amp setting for the extended periods of time required for the process caused the charger to overheat and turn off. A nifty safety feature.

(See the tape? Yep. It's there to keep the anode from tipping out of place.)

I let the set up run for 8-10 hours at a time between check-ins.

Step 5: Results

In between electrolysis sessions I would extract the sacrificial anode and clean it. Basically knock off the accumulated rust, dry it and sand it down a bit to remove the more stubborn bits.
I also replaced the electrolytic solution each time.

It definitely worked, but I wish I'd taken the time to do several more sessions.

As it is, I'm not planning on keeping the tank, so I wasn't too concerned at the time.



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53 Discussions

Smart chargers may need a battery between the charger and the tank. Charger Red Lead to Battery + post to Donor Metal (Anode). Charger Black Lead to Battery - post to Tank. If the water in the tank is not bubbling around the Anode, then something is not working correctly.

can someone tell me the difference if I use a 12v , 5amp, against 12v, 1 amp power source to perform this cleaning?

This Instructable works as described. Found Arm & Hammer Super Washing Soda ($5) and a .25" x 48" steel rod ($6) at Ace Hardware. I used my 1 amp and a 1.5 amp analog battery chargers. (Harleys have two half tanks.) My digital battery charger won't work on something that has no charge. I wish I had taken before photos. These images are from the second 24 hour period of cleaning. What I liked most about this is this process won't damage my paint job. Thanks jimbotheconflictor

2 replies

I used TSP powder instead of Washing Soda. The nice thing about TSP is the phosphate creates think black layer that is corrosion resistant. You can de-rust and rust prevention at the same time. It's not strong but at least you don't have to worry about flash rust at all. At the beginning of electrolysis you see orangish bubble, then it turns to grayish color. It means the de-rust is done.

I've read multiple articles on this method, and have been applying it to my tank, but one question remains:
Is there a way of telling that all rust has been removed without visual inspection of the metal itself? As it's pretty much impossible to inspect every nook and cranny...

I have some aluminum rods can i use this as anode?

Follow up from previous post: Here are the photos of the inside of the worse of the two tanks. After two cycles and the pressure washer at the car wash. Looks great! Can't believe that in 40 plus years of riding motorcycles I had never heard of this method of cleaning tanks. Never too old to learn.


Great info and a very nice set up you made for the electrode!

I had all kinds of trouble until I got the right battery charger. My "good" one wouldn't work for this unless it was also connected to a low (not dead) battery.


Doing this now on a '73 Yamaha. Made the soda from household baking soda by baking it at 350F for 30 minutes. Put duct tape over the tank outlet. It's been actively bubbling for 2 hours so far with a 1.5 amp charger. Made the electrode by putting some short hose sections on a piece of thin strap steel.

This is really interesting. I recently brought a 1972 Honda Cb350 that has been forgotten in storage since it was ridden down hhere (Florida) in 1977. Im about to begin tackling this issue. Tank is rusty inside. Dry, yet rusty. I don't think it's too gad though. I put a cup of gravel inside earlier amd shook the shit outta it, and w/ having only done that I can see the metal underneath. I am not sure yet if this is my direct route, but i will be putting.this into consideration. Thank you

I'm doing this right now on a 72 Honda CL100, its working great!

I was trying to remember how this was done thanks for posting.

FYI if you can't find washing soda just bake regular baking soda at 400
For 15 to 20 minutes the heat alters the soda to be more caustic.

A cheap source for sodium carbonate is the stuff pool supply stores sell for increasing Ph.

Want to make your own "laundry soda"? Take baking soda, spread it out onto a cookie sheet and bake it in the oven at a little over 300 degrees for an hour or so it will drive away a water and CO2 molecule thus making washing soda

Graphite from a pencil makes an excelent anode which never corrodes. Resistance for #2 pencil lead is about 1 ohm per cm, but that will vary based on thickness. The fatter the lead, the lower the resistance

The oxygen bounces harmlessly off of the graphite and exits the solution as O2 gas

A very useful article. The author of Respect.
Vladimir http://auto-eyes.ru