Instructables

Electrolytic Rust Removal From A Motorcycle Gas Tank

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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.

 
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Step 1: Materials & Tools

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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

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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

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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.)
jesucka876 months ago

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

Marfinhead1 year ago
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.
hdscarbro2 years ago
A cheap source for sodium carbonate is the stuff pool supply stores sell for increasing Ph.
chesterjohn2 years ago
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
babah4112 years ago
A very useful article. The author of Respect.
Vladimir http://auto-eyes.ru
waldosan2 years ago
it seems like a pretty solid concept, i'm sure it worked, i might have to try it myself just on like some scrap steel to make sure it works. does the baking soda have to be the "super washing soda" or can it be just regular baking soda?
eosgood3 years ago
Great set up. I plan on applying the same method to my tank tomorrow. I am being cautious because my tank is terribly rusted and I want to avoid making it worse.

Most importantly, I am concerned about re-rusting. Not many of rust removal solutions address this. For example, there are many forums that say to use vinegar, acetone, or muriatic acid etc. All of these, unless successfully neutralized, would temporarily remove oxidation but accelerate the rusting process.

I am sure electrolysis poses less rust potential than acid based solutions. However, what is the proper procedure immediately following electrolysis?

Rinse with denatured alcohol? Rinse with soapy water? Rinse with diesel fuel or gasoline? Rinse with WD-40? Does the tank HAVE to be sealed with something such as Kreem?
chip123 eosgood2 years ago
I've heard that the best thing to do is rinse the tank with some diesel to stop it rusting again after de rusting the tank. Alternatively, just keep the tank filled up with petrol (gasoline).
Keeping the tank filled helps, but isn't a perfect solution. With changes in temperature and pressure, air laden with water vapor enters the tank, condenses at night when it gets cold, and the condensate drops to the bottom of the tank, since it is lighter than diesel or petrol. Once trapped beneath a layer of fuel, the water doesn't evaporate, and as the expand/contract/condense cycle repeats over days and weeks, the amount of water that accumulates in a stored vehicle/boat/airplane fuel system can become quite impressive.
After using acid, rinse with a baking soda solution. For something as small as a motorcycle fuel tank, a small box of baking soda from the grocery store should suffice. After the baking soda (sodium bicarbonate) has neutralized the acid, follow with a deionized water wash, then dry thoroughly. If there's a store that sells distilled water, you can use that as a rinse; next-best is reverse-osmosis filtered water. Use low pressure compressed air or a warm stream of air from a pistol-style blow dryer to get the moisture out of the tank before it can rust again.

You can get a fuel tank sealer kit from the Eastwood Company (http://www.eastwood.com) that is as simple as pouring the liquid in, sloshing it around, pouring the excess out and letting it dry. Considering that most steel fuel tanks are originally protected by a zinc coating inside when new, and after you've removed rust the coating is almost certainly gone. the plastic sealer coating is essential to preventing new rust formation.
bherrboldt2 years ago
Ya sure would like to see the finished tank. Cause I would like to clean a couple tanks I have lyin around.
william13703 years ago
Grroosss. Thats a lot of rust!
I miss my 76 Honda 550F Supersport !!!!
Techcowboy3 years ago
That's great and all, but why is there no picture of the tank after you were done? Am I missing it?
Nyxius4 years ago
Increasing the ion concentration increases the ability of the fluid to transfer charges. 2 lbs of soda is approx. the limit of solubility per gallon. I would like to warn you that this process strips actual metal off along with the rust. This particular reaction can be augmented by pouring Peroxide into the final solution. This will remove the last vestiges of carbon dioxide and will form sodium hydroxide (which is much more effective/efficient). You might want to balance the equation with your concentration to find the right amount. Speaking from personal experience I find that acetic acid is a much more effective electrolyte since most salts of it are water soluble. once your rust is cleaned out be sure to remove the acid and rinse with denatured alcohol to prevent re-rusting. Also, you can replace the electrolyte and put in a copper cathode to re-coat the tank with copper oxide. Coating the tank with copper oxide should help prevent any future rust problems. It would be better if you plate it with copper. You can't electroplate anything with a car charger because the voltage is way to high and it oxidizes your plating material.
Please explain more about the copper plating and not being able to use a battery charger. Can you use a charger to plate with copper or is the voltage too high? Any suggestion on a voltage source? How about 6 voly charger?
The voltage potential on most chargers and batteries are way to high and will cause the water in the solution to breakdown and oxidize anything it can find. 6 volt is better but you are still going to have poor results. the best thing you can do is string a bunch of 1.5 volt batteries in parallel since it is the amperage that increases the speed of the reaction/depth of deposit. 12 D cells in parallel should be enough. if you are going to plate this way you should also try to keep the fluid moving and hot. I have had to improvize for most of my reactions. But I was using a glass chamber so my tech won't work for you. If you don't keep it moving formations resembling corrosion will start to form. These are not, they are actually metal deposits forming in potential hotspots. you could try running a transformer in reverse with pulsed DC to achieve the required voltage/amperage. Think of it this way... you are using electrons from your source as a part in your chemical reactions. the more there are the higher the density/speed of reaction.
ensoarts Nyxius4 years ago
Could this process be used to plate both the interior and exterior with copper?
Thanks for the help!!
Thanks for the response!!
XaqFixx4 years ago
Thank You for this instructable. I am going to be resurrecting my dad's 1972 CB175, which has been sitting in a barn since 1976, and converting it into a cafe rat and this will be a big help.
Rainh2o4 years ago
Also seen people do this to old antique tractor and car parts that where totally rusted together, like pistons to engine block. Takes awhile but you can remove them without a lot of damage.
Rainh2o4 years ago
I've done this with cast iron pans that where "beyond use" that people throw out. It strips them to bare shiny metal if you have the patients. Also copper plated things by reversing the polarity and using a chunk of copper as the anode.
Do you have any "after" photos?
That would be nice wouldn't it? I didn't have access to the camera after the final session and moved on to applying Kreem (another first) right after I drained the solution and rinsed w/ acetone.
Kreem is some kind of sealant I assume? I'm currently building up a moped, so this sort of thing is interesting to me.
you may wish to visit mopedarmy.com you will find loads of useful information there.
yup: http://amzn.com/B001J0DHZK
tkjtkj4 years ago
Nice 'structable' .. but based on my experience in the aircraft industry, you'd best consider purging that or any gas tank of all 'sequestered' gasoline! Eg, before anyone can weld a gastank, federal regs *require* not only that it be purged, but how to do it: many hours by running hot water thru the tank, less time (i forget how much) if its purged with steam .. The combo of gasoline vapor (even in an apparently 'empty' tank!) and the possibility of a spark is begging a very unhappy event.
mdog934 years ago
So is the washing soda just adding bicarbonate of soda as the salt in solution or what salt is it?
dchall8 mdog934 years ago
Washing soda (sodium carbonate) and baking soda (sodium bicarbonate) are different things. Washing soda used to be easy to find in every grocery and pharmacy but is getting harder to locate.
Nyxius dchall84 years ago
Sodium Carbonate can be made out of sodium bicarbonate by either directly heating it (thereby releasing CO2) or by boiling it (same diff but more controlled).
mdog93 dchall84 years ago
oh ok, i just knew that bicarb. of soda has very good anti-stsaining properties, so is used in a lot of natural cleaning products nowadays.
jimbotheconflictor (author)  dchall84 years ago
You have to look on the top shelf.
rimar20004 years ago
Very interesting. I think maybe you can galvanize the inner of the tank, replacing the sacrificial anode with zinc and reversing the polarity.
jimbotheconflictor (author)  rimar20004 years ago
Do you mean galvanize instead of removing the rust, or galvanize after removing?
After!
Nice rig - sweet and simple. Looks like it worked very well too - I've seen people go nuts with microwave transformers, arc welders, etc. I like it.