polyethylene or aluminum gas tank?

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mrdeepseafisher

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I want to install new gas tanks in the boat and have always had aluminum. Are the polyethylene tanks as safe as aluminum? I think they might be lighter than the aluminum which is why I am considering using them.

Any comments appreciated.

Lee
 
I'd go aluminum hands down, especially if we start to see ethanol in marine fuel...

Good luck!
 
I'm not gonna argue with these two guys. They are experienced.
I think if I were you, I'd contact a Mfg of tanks and ask him.
Then I'd contact the Fuel folks and ask them.
Then, I'd contact a chemist who works with Poly-etc (there's a bunch of them) and ask him.
My reasoning is this: There must be a logical reason to do one or the other, or not to do either!
Of course it's gonna be a Chemist who has the right info.
 
Note that i believe that the EPA has been considering banning poly/UHMWPE due to what amounts to osmotic leakage. ie: some of the lighter components of gasoline can "weep" through the plastic. I did notice an odor from mine, and tend to agree that the issue may exist.

Each has it's strengths and weaknesses. Aluminum, of course, can corrode...
 
Okay so I am a chemist who works on and with plastics, including HDPE. HDPE is no problem with E-10 gas. Your car's tank is probably HDPE. Aluminum's basic advantage is it is lack vapor permeation and ability to get tight, machine quality fittings on it. HDPE's advantage is durability to getting bumped and handled along with corrosion resistance. If it is an enclosed space below decks I would go with aluminum. If it was in an open environment like on-deck, I would go with the HDPE tank. If you choose aluminum be sure it is well coated with an aluminum compatible coating and has air space all around. If you choose HDPE, avoid direct sunlight exposure as much as you can.

edit added - after thinking abut this for more than a few minutes it dawned on me that there is probably an ABYC standard on fuel tanks for enclosed spaces. My suspicion is that poly fuel tanks are probably verboten, but I don't really know. You should post this question in "The Marine Surveyor" forum.
 
When Powerboat~Reports was still around, they recommended poly over aluminum hands down. But that was before they were putting so much methane into the gas. I'd see what USCG or UL require and use that.
 
I have a HDPE tank in my SeaRay 270DA. I had some vapor issues, but what I found was the gauge sensor was not properly sealed. I got a new gasket and used a permatex product made for sealing fuel against HDPE and my problems ceased. It is a very tight system. I also don't worry about corrosion. I'm very happy with the tank. Ditto Flutterby on the PBR articles. They would down a boat a few points if it did not have a HDPE tanks. You can use HDPE in an enclosed space.

Here is the sealer I used:

http://www.permatex.com/products/Au...atex_Ultra_Rubber_Gasket_Sealant_Dressing.htm
 
However, my 17 yr old boat has an aluminum tank----properly installed. I have yet to have any probems, but it always stays dry, and I inspect it every time the engine hatch is open. I also have a fume detector just in case.......
 
I have gotten back a few replies from custom tank manufacturers and it looks like they recommend aluminum tanks with an epoxy coating.

I guess this is what I'm going with.
 
Here's the reply to a question about plastic tanks that was posed to Moeller, a major supplier to the boating industry. It's reprinted with permission from another boating forum. Note how ethanol affects the expansion and contraction of non metal parts other than the tank itself. We had the pickup tubes on six gallon tanks used on rental boats at work shrink and split and drop off leaving boats stranded.

"Are you aware if (boat mfg name omitted) fuel tanks and parts of the fuel tanks can and will withstand the use of E-10 ethanol fuel?"

Answer:
The Energy Policy Act of 2005 requires ethanol production to nearly double in the US by 2012. The EPA, which is responsible for setting Federal Guidelines that regulate fuel content, is allowing a 10% ethanol and gasoline blend for common engine use: percentages higher than E-10 are currently prohibited. The potential effects of E-10 and E-85 fuels on existing marketed products remain one to be wary of:

1. Ethanol is hygroscopic, mixing more easily with water than gasoline.
Fuel Tank Shell will not be impacted.
May lead to serious damage to some fuel system components- regular
maintenance recommended.
2. Ethanol increases fuel electrical conductivity.
Promotes metal corrosion of system components
Most of the "molded in inserts" are encapsulated thus a non-issue.
We are waiting to hear back from our sending unit companies to validate their senders are E-10 compatible.
3. Ethanol blends, such as E-10 affect the integrity of some gaskets and other non-metal materials.
Can cause common materials to swell in excess of 35% and shrink by 6%.
Already working on improving our pick-up tube material to provide
greater compatibility with blends.

With this being indicated fuel systems going forward will need Water separation filters, which Moeller Marine can provide. This will reduce and minimize Ethanol related issues."
 
Ethanol is gasoline is not an issue for a HDPE tank. However, it has and may challenge other fuel system components. This is all well known.
 
I dont know what the plastic 6 Gal tank for my 25 Hp Mariner is made of, but the sun is doing a helluva lot more damage than the fuel is.
I have no idea if the Fuel they sell up here in 'these hills' is Ethanol though.
 
Thud, no one over there would put perfectly good shine in a fuel tank... ;)
 
we have had to replace or put new bottoms in 4 boats with aluminum fuel tanks one was a 1998 pennyan all had corrosion issues mostly from the outside often where they touched wood that remaind wet or damp all the tanks were unpainted
 
quote:
Originally posted by mrdeepseafisher

I have gotten back a few replies from custom tank manufacturers and it looks like they recommend aluminum tanks with an epoxy coating.

I guess this is what I'm going with.

Click to expand...


Some claim the paint can be a negative, if it flakes and water gets under it. Pascoe's site may be one place I read that. I'm about to order some aluminum tanks as well. The marine fuel tank place up here in MA, suggested the "Rhino-Liner" stuff they use in truck beds as an alternative. Apparently several of their customers have brought their tanks to a place nearby that does this. Suggestion for the poster. Opinions from others? A few more bucks to guarantee a good lifespan's ok with me.....

Regards,
Mike
 
quote:
Originally posted by Grady Wahoo

quote:
Originally posted by mrdeepseafisher

I have gotten back a few replies from custom tank manufacturers and it looks like they recommend aluminum tanks with an epoxy coating.

I guess this is what I'm going with.

Click to expand...


Some claim the paint can be a negative, if it flakes and water gets under it. Pascoe's site may be one place I read that. I'm about to order some aluminum tanks as well. The marine fuel tank place up here in MA, suggested the "Rhino-Liner" stuff they use in truck beds as an alternative. Apparently several of their customers have brought their tanks to a place nearby that does this. Suggestion for the poster. Opinions from others? A few more bucks to guarantee a good lifespan's ok with me.....

Regards,
Mike

Click to expand...


Use a coating made for the surface, in this case aluminum. The truck bed liners were made to go on over polyurethane paint. Personally, I would go with an epoxy coating for an inboard installation. The chemical resistance is excellent and so long as the surface is properly prepared you won't beat it.
 
If you are painting aluminum, you have to etch it, alodine it then paint it. Anything else is a waste of time. If I was doing an aluminum tank, I would first etch, alodine, then I would paint it with Akzo Nobel epoxy primer. We use this stuff underneath the lavs on the jets where urine and sewage often leaks.

http://www.aircraftspruce.com/pdf/2008Individual/Cat08347.pdf
 
I'm glad we have Eric here. Need some clarification.

First, I heard there was a problem with coal-tar epoxy and aluminum. Something about graphite or carbon?

From a few years ago, when ethanol was first talked about and only introduced in some areas, there was a report that said Poly wasn't affected by E10 but said there was no guarantee with higher levels of ethanol....SO! Now it's safe?
 
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