Pitted fuel tank--looks like salt water pitting

R

Renken19-California

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31 gallon fuel tank in the belly of my Gulfstream. I pulled the tank. I found 4 pencil eraser sized rot holes. Maybe 20 or so pin sized holes.

I used JB weld to fill the holes. Any other ideas short of replacing this tank?

Fiberglass the bottom?
 
Grub54891

Grub54891

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Re: Pitted fuel tank--looks like salt water pitting

I'd replace it,unless ya know a good aluminum welder that will do a fuel tank." I assume its alum" i wouldnt trust a jb patch myself. If it fails it could be deadly.....
Grub
 
tpenfield

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Re: Pitted fuel tank--looks like salt water pitting

Here is what my tank looked like when I pulled it out . . .

FuelTankInsp-08.jpg


those 'pits' were about 1/2 way through the thickness of the aluminum. I was concerned that even with JB Weld, the 'pits' may continue to grow and eventually form a hole in the tank, leading to a hazardous situation.

So I replaced the tank . . .

IMG_0359.jpg


You may want to consider a replacement tank, as patching corrosion areas is a crap-shoot.
 
R

Renken19-California

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Re: Pitted fuel tank--looks like salt water pitting

What would happen if I fiberglassed the bottom of the tank, (outside) would it hold?
I have lots of pits, but only 3 tiny leaks. From salt water, this boat will be used only in fresh from now on.

I priced a tank $$$$
 
tpenfield

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Re: Pitted fuel tank--looks like salt water pitting

Fresh water is what causes the pits . . . it is corrosion that occurs on aluminum when continually exposed to water (either fresh or salt). fiberglassing the tank will probably cause more water to be trapped against the tank's surface as the fiberglass will separate from the tank and provide a place for condensation to get trapped. The tank will probably die a more violent death at some point.

US Coast Guard and other associated regulations are pretty stringent regarding aluminum tanks. There are always plastic tank alternatives, but those tend to 'smell' like fuel after a while.

Yes, the tanks are expensive, but a failed tank can lead to a tragic situation . . . how much is your life and the life of your crew worth.?

I paid $1K for my new tank.
 
tpenfield

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Re: Pitted fuel tank--looks like salt water pitting

I'd also say that if you have actual leaks in several places on the tank . . . it is ball game over. You could never trust the tank with patches, etc.
 
Grub54891

Grub54891

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Re: Pitted fuel tank--looks like salt water pitting

Not to steal the thread but, my alum tank is in beautiful shape,the rest of the boat was rotted,wet foam,the whole mess. Rebuildig now. If fresh water corrodes a tank why is mine ok?
Grub
 
R

Renken19-California

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Re: Pitted fuel tank--looks like salt water pitting

I'm so tempted to try POR 15 or like product. But my need to be exploded into tiny bits or burned to a crisp like bacon is not high on my todo list

I have a larger tank that is in good shape given to me by a shop here locally. I would need 6 inches cut off to fit the belly. I'm going to find a shop and price a fab modifier for the free tank vs this pitted one
 
tpenfield

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Re: Pitted fuel tank--looks like salt water pitting

grub1grub2 said:
Not to steal the thread but, my alum tank is in beautiful shape,the rest of the boat was rotted,wet foam,the whole mess. Rebuildig now. If fresh water corrodes a tank why is mine ok?
Grub
Click to expand...

There are a few publications on tank corrosion on the Internet. A salt environment is certainly more prone to corrosion, but fresh water also has its history of occurrences (minerals in the water) . So, perhaps your situation is one of the more fortunate ones. . . .

It sounds like this boat in question was used in salt water for a while :noidea: So the mineral content is probably still there. I have also seen some articles about ethanol contributing to corrosion.
 
R

Renken19-California

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Re: Pitted fuel tank--looks like salt water pitting

I'm in Monterey. I have several stern drive boats. Most have the tank up behind the rear seats. I picked this Gulfstream up on the cheap. It is in good shape but was sucking water into the carb. It took us a week to begin to figure out it was NOT where we are buying fuel, but water in the belly and leaks...
 
NYBo

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Re: Pitted fuel tank--looks like salt water pitting

tpenfield said:
I'd also say that if you have actual leaks in several places on the tank . . . it is ball game over. You could never trust the tank with patches, etc.
Click to expand...
^This
 
P

pevaguy

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Re: Pitted fuel tank--looks like salt water pitting

If all the corrosion is in one area, you may be able to "plate" it, have a patch welded over the corrosion area if the rest of the tank is sound.
 
R

Renken19-California

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Re: Pitted fuel tank--looks like salt water pitting

Naw its a lost cause. For hoots and giggles I plugged some of the holes, then put fiberglass over it. Let it dry and filled the tank with water
Seepage.

Too many pinholes. I have a tank that was given to me that is 4 inches too long. I am not going to cut the center brace to fit this one in, so tomorrow I will find a shop to cut this other tank down to size, so to speak.

O well we live and learn:laugh:
 
8

81_chapparel194

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Re: Pitted fuel tank--looks like salt water pitting

tpenfield said:
I have also seen some articles about ethanol contributing to corrosion.
Click to expand...

next you guys are gonna be blaming the beginning of ww2 on ethanol or global warming. people all ethanol is is a slight variation of mountain brewed moon shine. it has a superior cleaning quality. that's the biggest issue with the dirty carbs is that the ethanol is cleaning all of the sludge from the tank. the fuel itself is perfectly ok. I run ethanol (10 %) in my vehicles 08 dodge ram, 02 mustang , my fuel injected motorcycle and yes even my boat. and 4 wheeler and lawn mowers. with ZERO problems. I will agree on phase separation but again I don't let nothing set up long with the fuel in it. I live in the south so I can boat year round and ride my motorcycle year round. so as long as you plan to keep it running frequently you have NO issues. at times I run e 85 (85%) ethanol in my truck when its available.
I swear yall act like this suff is a magic corrosive acid that will instantly dissolve your engine. same way with sweet water boaters thinking that just getting near salt water will instantly dissolve your trailers and seize up your engines. smdh ok off my soap box now iknow I will catch some slack for this but its ok I can argue my point with proof to backit up. so I don't care of your mechanic told you this stuff was terrible. he just heard it from his ol man that said the same thing about computers..
 
tpenfield

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Re: Pitted fuel tank--looks like salt water pitting

Didn't the ethanol bomb bring an end to WW2 :noidea:
 
H

Home Cookin'

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Re: Pitted fuel tank--looks like salt water pitting

tank holes also come from places where the tank rubs against a pressure point. I also have to wonder if there isn't some electrolysis going on from the sending unit.

a specific leak such as from a rubbed spot could be fixed but if it's bird-shot, it can't be fixed safely. take the first holes as warning shots.
 
dingbat

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Re: Pitted fuel tank--looks like salt water pitting

While it may seem logical to draw the conclusion that the salt water must be corrosive to the aluminum, it is not. Salt water does not corrode aluminum because of its neutral pH. A saltwater solution can, however, be a major facilitator for galvanic or dissimilar metal corrosion, a more complex corrosive process.

Aluminum owes its excellent corrosion resistance to the barrier oxide film that is bonded strongly to its surface and, that if damaged, re-forms immediately in most environments. On a surface freshly abraded and then exposed to air, the barrier oxide film is only 1 nm thick but is highly effective in protecting the aluminum from corrosion. Remove the source of oxygen. i.e. stagnate water or moisture, the oxide barrier can not replenish itself and corrosion begins.

Some manufactures use rubber “cushions” under the tanks. Moisture trapped between the rubber and the tank causes problems. Pressure treated wood is a known source of problems as are dissimilar metals.
 
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