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Author Topic: Electrolysis to clean-up a rusty motorcycle gas tank  (Read 1693 times)

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Mtl dummy

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Electrolysis to clean-up a rusty motorcycle gas tank
« on: October 03, 2018, 02:09:19 PM »

Hi all
I am a gearhead with no knowledge of chemistry. I don't even remember the difference between covalent and polar-covalent bonds (high school in the 80s). IE my chosen username is accurate.

There are piles of youtube videos on the process of using water and baking soda with a battery or trickle-charger so my question is about silicone or any material that will survive inside the tank during the process.

I stripped-off the guts of the fuel pump so just this piece will be inside during the process. The black plastic 'block' circled in red is what concerns me. This will be inside the water / soda solution for the duration of the process.



Will the electrolysis react poorly with plastics in general? Being paranoid, I'd like to completely COVER it with a big glob of silicone, since it's easy to cover an odd shape like that.. .and will also be easy to remove afterward. Will electrolysis react poorly with silicone?

Knowing what I'm trying to do, if electrolysis harms plastic, is a big blob of silicone viable? If not, does anyone have a simple solution for a doofus like me, with readily-available materials?

Any help is greatly appreciated so thanks in advance!

André in Montréal
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Borek

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Re: Electrolysis to clean-up a rusty motorcycle gas tank
« Reply #1 on: October 03, 2018, 09:37:08 PM »

No simple answer - some plastics are quite resistant, some are not. It is not electrolysis that is a problem, rather the electrolyte that is corrosive. The only sure way is to test the plastic before applying the process (yes, I know it is rather difficult when you have just one piece).
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Corribus

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Re: Electrolysis to clean-up a rusty motorcycle gas tank
« Reply #2 on: October 04, 2018, 02:24:07 AM »

Is there any way for you to determine what polymer the component is made of? Is there a recycling symbol on it? Is there a manufacturer you can call?

Most polymers are resistant to this kind of corrosion, and I would wager any polymer used for a part like this probably would be, but it's impossible to know.

Is the part typically exposed to the elements? (e.g, rain water). If that's the case, you could probably infer that it will be made of a corrosion-resistant polymer.
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Mtl dummy

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Re: Electrolysis to clean-up a rusty motorcycle gas tank
« Reply #3 on: October 04, 2018, 03:22:23 AM »

Unfortunately, I cannot think of any way to inquire about the specific composition of such a tiny component of a motorcycle part so that's why I'm hoping to get a yay or nay on something that is theoretically easier to nail-down... like plain ol' silicone caulk.

Someone on a bike forum suggested RTV (gasket maker), which is more like a rubber in a tube, as opposed to silicone in a tube.

Another person has said to forget the electrolysis and use cider vinegar.... the internet is so full of different opinions lol. This is why I thought to seek out opinions here from people who are smarter than me and who actually understand what's going on in these processes!

So do silicone or rubber remain stable when exposed to electrolytes?

Come to think of it, barring a verdict on silicone here, this could be tested in advance. I could simply rig-up an electrolysis setup specifically to observe what happens to silicone and RTV in a controlled environment... NOT inside my gas tank!

Maybe one suggestion please? I'm used to creating precise solutions of plain old table salt and sodium nitrite to brine meats so that being said, what would be a good target 'concentration' (like the salinity in one of my brines) of sodium carbonate to water? It is sodium carbonate and not sodium bicarbonate, correct? It's no fun being uneducated :(

A big thanks to all.
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Corribus

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Re: Electrolysis to clean-up a rusty motorcycle gas tank
« Reply #4 on: October 04, 2018, 03:54:42 AM »

My physical chemistry professor back in undergrad had a saying that stuck with me: one experiment is worth a thousand theories. Sometimes it's easier just to play around and see what happens than try to predict the best conditions beforehand. Although the part in question is precious, the robustness of the silicones and rubbers you are considering using is easy enough to test in isolation. So that's a great place to start. Make sure to test them at the worst possible conditions you will use. For example, if your electrolysis process will be done at room temperature for ten minutes (just as an example), do a thirty minute test.

As for the conditions - sometimes there is no right answer, which is why there are so many recipes floating around. Baking soda is sodium bicarbonate. The difference between carbonate and bicarbonate largely comes down to the alkalinity of the resulting solution for identical concentration - carbonate will give you a more caustic solution. The carbonate is a better electrolyte, but bicarbonate is usually easier to obtain. Carbonate is often called "washing soda", so if you can find it, I'd probably recommend that over baking soda. In a pinch you can make your own by baking, er, baking soda in an oven for a while at moderate temperature.

PLEASE DO NOT USE TABLE SALT. You can form chlorine gas, which is no bueno.

I googled electrolysis for engine part cleaning and indeed found a number of recipes. The first one I clicked on was: http://antique-engines.com/electrol.asp
Seems as good a place as any to start. Although the concentration matters, for the most part it will come down to kinetics (speed of the process). The product (cleanliness) is largely a matter of aesthetics so there's no real wrong option here. If you start at a lower concentration and the results aren't good enough, increase the concentration and try again. Since you have some plastic parts you are concerned with, maybe start with a lower concentration and work your way up until the metal parts are clean enough to your liking. Better to have to try again than to overkill it and destroy your components.

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