Ethanol and aluminum tanks

With E85, yes, but E10???

 

Absolutely! It's all about the separation layer...10% is plenty for that.

 

So what can we do about sealing our tanks to prevent damage? Anyone ever open a tank to see what's inside?

 

Boat article but it applies.


The National Marine Manufacturers Association (NMMA) opposes the use of marine fuels that contain greater than 10% ethanol content by volume. This position is based on safety and durability concerns and supported by many well documented studies.

According to state boating registrations, there are over 12 million recreational boats in the United States. Boat builders utilize five types of materials to fabricate fuel tanks. These are aluminum, steel, cross-link polyethylene, high density polyethylene and fiberglass. For a rough estimate of today’s numbers, there are approximately four million boats that have aluminum fuel tanks; approximately seven million have steel or polyethylene tanks, and less than one million have fiberglass tanks. The data clearly indicates that the increased use of ethanol in gasoline has raised safety and durability issues for aluminum and fiberglass fuel tanks.

Aluminum Fuel Tanks

In the case of aluminum tanks, aluminum is a highly conductive metal that relies on an oxide layer for its corrosion protection properties. Low levels of ethanol, such as E10 (10%), are usually not a problem in aluminum tanks because the oxide layer provides a good measure of protection. The problem occurs when the ethanol content is increased.

There are two mechanisms that occur with ethanol. Both mechanisms are a result of the hydroscopic property of ethanol, meaning it absorbs water. The more ethanol in the fuel, the more water there will be in the fuel tank. Water not only causes the tank to corrode, it also causes the corrosion particles to clog fuel filters, fuel systems, and damage engine components. The corrosion rate can be accelerated under a number of conditions if other contaminating metals are present such as copper which may be picked up from brass fittings or as a low level contaminant in the aluminum alloy. Chloride, which is a chemical found in salt water, will also accelerate corrosion. In the long term, corrosion can perforate the aluminum to produce leaks that would cause fuel to spill into the bilge and end up in the environment. In the worse case it could cause a fire and/or explosion hazard. Boat fuel tanks are often located under the deck next to the engine where the operator might not be aware of a leak until it was too late. .

The second mechanism that can occurs with the increased use of ethanol based fuel in aluminum tanks is galvanic corrosion. Gasoline fuel is not conductive, but the presence of ethanol or ethanol and water will conduct electricity. The galvanic process that occurs to aluminum trim tabs, stern drives, shaft couplings, etc. will occur within the aluminum fuel tank. Boat builders are able to protect exterior aluminum boat equipment with sacrificial anodes known as zincs. Sacrificial anodes are not a feasible option for the interior of a fuel tank.

 

So,
Is corrosion happening all of the time or only when there is phase separation?

 

Wonder if that fuel additive that negates the effects of the ethanol (there is a marine grade additive) would work??

 

FYI, the bottom floor of one of my 246GT aluminum tanks before restoration, and i've only used super fuel (E10). We did not notice any holes before we removed all of the paint and there it was.
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How was it repaired?

 

Welded in new hand made bottom panels. I'll watch these more closely from now on and will try to always have fresh fuel or drain, learned my lesson.
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This is a topic that people need to be more aware of. If you have access to pure boat gas without ethanol that would be ideal but around here that's over $5.00/gal. I know the marine guys are not crazy about the additive to neutralize the ethanol. So what's the best answer?

 

I think the only option is to use the car and cycle through fresh gas. Store the car mostly empty in a climate controled space and some day line the tanks.

 

In CT we have been using E10 since 2005. I have not experienced any problems with tanks or fuel line in any of my 4 vehicles. Three of them, including my 85 308 and my 03 Z4, are stored 6 months out of the year. The fourth (my pickup truck) usually sites for a few weeks between useage. I have never added stabilizer or bothered to store the cars with full or empty tanks. I just park them for the winter (or summer in one case) and forget them.

After reading this E10 parinoia, mostly on F-chat, I started some experiments last fall. I stored gas in variois containers (glass, plastic, aluminum) which were vented to the atmosphere so that air/humidity could enter the containers as the weather changed. It is going on 5 months now and in no case have I oberved any separation. Just recently the two cars which have been in storage were started. They started without problem, just as they have every year. I'm not going to start worrying about it now.

 

I'm going to run my tank low and put my bore scope in it. Do I need to worry about an explosion from the little light in the in the end of the scope?

 

Ethanol free gas this is what i use for the last 3 years just check the web for a station near you,i use shell it burns cleaner and hotter.

 

Here in MA all fuel contains ethanol.

Anyway,

When it comes time to do the rear bushings i'm taking my tanks out and sending them off to this company or any other that uses RENU. That way I can live worry free for years.
http://gastankrenu.com/
http://www.gas-tank.com/

 

Excellent work!

This is an excellent idea. Only way to tell otherwise is to see weeps on tank paint and gas smell.

I have to agree here. I was thinking about tank removal myself, but suspension removal looks like a requirement. The bore scope is the best plan. I may get one myself.

 

As others have mentioned in the past, the challenge with coating the inside of the 308 tanks are all the internal baffles. I'd be interested to know if these guys can work around that.

 

I'm trying to figure out what they look like inside.

 

I have used their other plating stuff but not this. I read the instructions and it would be tough to do at home due to the disposal of the hazardous materials left over. I would still consider it though...We have hazmat drop off once a year in my town.