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Ethanol and aluminum tanks

D

David-aviator

Well Known Member
Some time ago it was reported that ethanol may be corrosive to aluminum. At the time I looked inside the fuel cap opening and observed that my tanks appear quite new and shiny after using up to 10% of the stuff with mogas for some 4 years with the Subby.

Today I arrived at the point where it was time to check out the fuel system with the Lycoming install but before pouring some 100LL into the tanks, which have been empty for a few months, I had another look at the condition of the skins. Wow, they are not new and shiny looking anymore.

There was a film on the skin surface that could be removed with a rag on a stick. The substance that came off with the stick and rag was black. After fuel was poured in, the tanks looked new and shiny like before. The film, whatever it is, is only visible when the tank skin is dry.

I do not know what the film is. It could be corrosion or something different. In any event, I am off the ethanol kick. From here on it will be mogas without the stuff or 100LL.



 
Question

Are you sure the film was caused by ETOH?..Seems a bit drastic if you have been quite happy with 10% mix in the soob.

The material compatibility issues notwithstanding.

Frank
 
Residue

My guess is that it is a form of residual "shellac" that happens with most all very old mogas as found in old lawn mowers etc. The fact that you probably drained all the gas before storing probably prevented a lot of sticky goo in the bottom of the tank and the lines.

Of course as usual I have been wrong before!;)
 
Sounds like you have some of the heavier petroleum distillate carryover from the refinery. Not uncommon, it's basically a light wax that is dissolved in most fuel, and will deposit on the sides of the fuel tank as the fuel evaporates. New fuel will dissolve it again, and it burns just fine. Ethanol exposure (or lack of) is not the cause of this. This the main component of the "shellac" or "gum" associated with old fuel, and is more plentiful in lower octane mogas versus premium mogas.

The clue is the fact that you rubbed off a dark substance on your rag - ethanol tends to oxidize the aluminum surface to a much deeper level than you would otherwise see, which results in a whitish chalky layer on the surface that does not disappear when wetted with fuel. Alodining (or anodizing) all the fuel-wetted aluminum surfaces will protect you from ethanol-induced corrosion effects.

Feel free to stay away from E10 if you like - but this is not the corrosion you would see if E10 were at fault.
 
Last edited:
airguy said:
Sounds like you have some of the heavier petroleum distillate carryover from the refinery. Not uncommon, it's basically a light wax that is dissolved in most fuel, and will deposit on the sides of the fuel tank as the fuel evaporates. New fuel will dissolve it again, and it burns just fine. Ethanol exposure (or lack of) is not the cause of this. This the main component of the "shellac" or "gum" associated with old fuel, and is more plentiful in lower octane mogas versus premium mogas.

The clue is the fact that you rubbed off a dark substance on your rag - ethanol tends to oxidize the aluminum surface to a much deeper level than you would otherwise see, which results in a whitish chalky layer on the surface that does not disappear when wetted with fuel. Alodining (or anodizing) all the fuel-wetted aluminum surfaces will protect you from ethanol-induced corrosion effects.

Feel free to stay away from E10 if you like - but this is not the corrosion you would see if E10 were at fault.
Click to expand...

Thanks for that observation, it makes sense.

The skin under the film is in very good shape, almost new looking.

It's always good to hear from someone who knows the science behind what is going on.
 
About using mogas...does anyone use "Stabil"? or other gasoline treatment purported to reduce formation of shellac and bad stuff in aging fuel? Results?

Also, I noticed recently an Stabil advertisement proclaiming an new product formulated specially for mogas with ethanol in marine applications. Wonder if that would be worth considering in our aircraft? What say you guys? Any thoughts, knowledge or experience in this realm?

Dave.
 
DaveWelch said:
About using mogas...does anyone use "Stabil"? or other gasoline treatment purported to reduce formation of shellac and bad stuff in aging fuel? Results?
Click to expand...

I use Sta-Bil in my outdoor stuff (mower, pressure washer, generator, snowblower). Everything starts easily after the off-season.

No experience with mogas/Sta-Bil in an aviation capacity...
 
StaBil

DaveWelch said:
About using mogas...does anyone use "Stabil"? or other gasoline treatment purported to reduce formation of shellac and bad stuff in aging fuel? Results?

Also, I noticed recently an Stabil advertisement proclaiming an new product formulated specially for mogas with ethanol in marine applications. Wonder if that would be worth considering in our aircraft? What say you guys? Any thoughts, knowledge or experience in this realm?

Dave.
Click to expand...

Dave,
I have not used it in aircraft. However, I use it in any gasoline powered device which does not operate regularly. I once placed it into my 900cc Ducati, which did not run for four years. After changing the oil and installing a new battery, the bike started right up on that 4 year old gasoline. StaBil is great stuff.
Charlie Kuss
 
Yup, I put Stabil in every one of my gas cans before I go to fill 'em. I use it in every mower, string trimer, pressure washer, leaf blower, chain saw, mulcher and vehicle I'm not going to drive for a while. (Between engines taht are running and those that I'm "going to "ix someday", the ol' cylinder index is getting way up there!) Never had a problem starting again after the "off season". Hard to imagine that it wouldn't be beneficial to our Rotax's, but I'm going to ask 'em if no one else has already!
I'll let you know what they say,
Dave.
 
Ethanol in tanks

All,

I talked to those folks using pure ethanol in their rv-3, 4 and 8 with lycoming engines and they told me othe only thing they did was change the injectors and I think they made a small mod to the distribution manifold. Evidently these folks have been using ethanol sine early 90's. Ck out this link.

http://www.ethanolairshows.com/
 
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