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Getting the Rust Out - a novel approach

Here's something different I found on the SOHC Honda list. Someone there appears to have found it elsewhere.

"I just came across this novel approach to gas tank rust removal in an antique outboard newsletter, and thought I'd share.

  • Fill the tank with water.
  • Take a piece of steel re-bar long enough to protrude out the top of the tank, and tape up the bottom 1" so as to insulate it.
  • Place a wide-mouth plastic funnel in the filler neck and put the re-bar in through the funnel, so the funnel and the tape insulate the re-bar from the tank.
  • Get a 10 amp battery charger, preferably one with an current (amp) gauge, and connect the negative clip to the tank and the positive to the re-bar.
  • Pour salt in through the funnel until the current climbs to 10 amps, and wait approximately 2 minutes.
  • Check the tank. Continue if necessary, but no longer than absolutely necessary.
  • Rinse the tank several times, and dry thoroughly. (perhaps some Dry-and-Go or WD-40 to displace the moisture would be helpful.
  • The idea is that you electroplate the re-bar with the rust from the tank walls. I haven't tried this yet, but I think I will. It sounds far more environmentally friendly than phosphoric acid."


One reader of the above sent me the following:


I ran across your web page doing a Google search for Gas Tank Sealant and thought that you might like to hear about my attempt to remove the rust from a moped gas tank using your "Fuel tank rust removal - a novel approach" procedure.  I pretty much followed your directions as written but I did make the following changes;

1.  Instead of filling the tank with water and then adding salt I filled the tank to about 3/4 full with a premixed salt and water solution.  I didn't measure the salt to water concentration, I just poured a bit of salt into a plastic jug, added water, capped it and shook it to dissolve the salt in the water.

2.   I connected and turned on the battery charger letting it run for about 30 sec or so.

3.  I added more of the saline solution a little at a time until the charger was supplying around 10 amps.  At that point I filled the tank to the top alternately using plain water and the saline solution.  Keeping the current draw around 10 amps (it actually got up to about 15 amps for a short time).

4.  I allowed this witches brew to cook for about 4 or 5 minutes.  I do mean cook because while it was cooking the action actually caused quite a bit of the saline solution to boil/bubble out of the tank filler spout.  I replenished the lost fluid a little at a time.

Note:  This bubbling causes a fair amount of mess so when I flushed the tank and did it a second time I placed a bunch of absorbent rags under the tank to soak up the overflow.  I would guess that a little less current for a longer time would create less mess and accomplish the same thing but I didn't try it)

5. As stated in the note above I thoroughly flushed the tank with water, wiped the iron rod off and repeated the process a second time.

The result was a tank interior that turned out bright and shinny with a few (all I could see through the filler neck) very light discolored spots and no visible heavy rust.

My next step will be to coat/seal the interior of the tank.

Thanks for the helpful instructions ! ! !

Article By: David J. Morrow

August 2001 

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