Fuel tank shelf life?

[GravyStain]

I've been reading a couple of odds and sods about fuel tank failures and the balls ache of removal and replacement. Some seem to suggest that a fuel tank will give you around 15 years then may start to spring a leak so to speak due to corrosion / other factors. The removal does look like a very serious job.

have you guys seen much of this, or am I just seeing worst cases?

Thanks.

 

[fred247]

Firsty it will depend on the material used to make tanks and how open to the elements the tanks are, sea boats tend to fare worst due to the salt in the atmosphere.
I have had three boats built in the 90' s with no problems ! HOWEVER the boat I have now has just had its tanks replaced due to corrosion, also built in the 90' s
The orignial Tanks were alloy, I had them replaced with S/STEEL the yard had to remove most of the saloon interior, cut out the old tanks, then make and fit new tanks. Then refit interior
TOTAL COST A SHADE OVER £10K.
So two tanks failed at 30 years, 6 tanks no issues, its a crap shoot, my tanks looked in good shape but had corroded on the bottom were it couldn't be seen

 

[GravyStain]

Firsty it will depend on the material used to make tanks and how open to the elements the tanks are, sea boats tend to fare worst due to the salt in the atmosphere.
I have had three boats built in the 90' s with no problems ! HOWEVER the boat I have now has just had its tanks replaced due to corrosion, also built in the 90' s
The orignial Tanks were alloy, I had them replaced with S/STEEL the yard had to remove most of the saloon interior, cut out the old tanks, then make and fit new tanks. Then refit interior
TOTAL COST A SHADE OVER £10K.
So two tanks failed at 30 years, 6 tanks no issues, its a crap shoot, my tanks looked in good shape but had corroded on the bottom were it couldn't be seen

Due to salt water ingress and blocked drain tubes?

 

[fred247]

No! Corroded from the inside - water in tank , previous owners never sludged the tanks, water laying in the bottom.

 

[kashurst]

Fuel tanks don't really degrade unless:
they are left with water inside the tank - which causes diesel bug issues and depending upon the tank material rots the bottom out from the inside. Could be rain water or sea water - caused by poorly fitted fuel filler caps or tank vents pointing upwards!
or
the tanks are mounted on a flat surface that traps water (poor design) - then you could get external corrosion.
When you start looking at boats - consider how easy or hard it is to access the top of the tank, take out the fuel sender etc so the tank could be flushed/cleaned. Unscrew the fuel fillers and inspect the seal (or not!)
Ideally see if the tank has any inspection hatches and or a drain sump that will coolect any gunk to be periodically drained away.

 

[Momac]

From observation of reported issues the fuel tank corrosion issues seem to be due to boats sitting unused for long periods or being lightly used but I have no hard evidence to support that.
I do think more regular use must help to minimise water in the tank by circulating the fuel through the filters.
An absence of drain points in the base of fuel tanks doesn't help.

 

[simonfraser]

is corrosion in aluminium tanks more likely if tank contains diesel and wet internally or when wet externally ?

 

[markc]

I had a Fairline 40 20 odd years ago and the fuel tanks were aluminium and a weld gave up at the bottom of one of the tanks. It was quite an effort to get it out and repaired. I later had another Fairline that had mild steel tanks that just sat below the air intakes for the ER, they had to be changed too.

 

[Plum]

is corrosion in aluminium tanks more likely if tank contains diesel and wet internally or when wet externally ?

If the tank is made from the correct aluminum alloy (marine grade) you should not have a problem. Mine is 21 years old and still perfect.

www.solocoastalsailing.co.uk

 

[volvopaul]

I've been reading a couple of odds and sods about fuel tank failures and the balls ache of removal and replacement. Some seem to suggest that a fuel tank will give you around 15 years then may start to spring a leak so to speak due to corrosion / other factors. The removal does look like a very serious job.

have you guys seen much of this, or am I just seeing worst cases?

Thanks.

The worst tanks I’ve seen of late are the ones in Fairlines , they seem to split or degrade on the welds mostly the alloy ones made by Poole Tank company .
Next time your buying take a look who’s made the tanks , seems odd that a year 2000 ish tank won’t last 17/18 years yet some of the old mild steel tanks are still going in some older Princess or Fairline models , I know that after being an owner of both .

 

[simonfraser]

hm one good reason for not filling the tank to the top and bouncing the boat about on the waves ?

 

[fred247]

If the tank is made from the correct aluminum alloy (marine grade) you should not have a problem. Mine is 21 years old and still perfect.

www.solocoastalsailing.co.uk

Not true, mine were marine alloy ok 28 yr s old but still corroded, and what about corrosion of alloy boats? if the conditions are right most metals will corrode.

 

[Bandit]

I am in the boat trade, we see many fuel tank problems, for this article lets stick to diesel.

Water in a fuel tank will encourage fuel bug to grow on top of the water below the diesel and on the sides and baffles, fuel bug by product is acidic and corrodes the inside of the tank.

Fuel tanks in older boats are often mild steel, problems corrosion from outside and from inside, as well as rust dropping off the inside of the tank. Damage prone areas on top of the tank salt water often from spray or air intakes, behind the tank's insulation matting , saltwater inside the sound insulation, under the tank where it sits on bearers or on woven strips which hold salt water, inside from fuel bug.

Next came aluminium, depending on the grade of aluminium some are more corrosion resistant than others, corrosion on welds, corrosion underneath from sitting on woven strapping or carpet that is wet with salt water and corrosion on the inside from fuel bug.

Then stainless steel a better material if fabricated in a decent thickness.

I had a 15 year old Fairline with steel tanks that rotted through on the top from the outside due to saltwater from air intakes sitting there.

We see a lot of aluminium tanks with corrosion on the inside the quickest was a 6 year old french mainstream trawler yacht, rotted out on the inside on the welds from corrosion from fuel bug.

All fuel tanks should have a drain at the lowest point or a sump and stripping line as well as inspection hatches, very few production line boats have any of these features.

Boat owners should strip out water from their tanks religiously and always use an fuel bug biocide, and if they have evidence of fuel bug in primary fuel filters have tanks and lines cleaned, very few do.

I have stainless tanks 19 years old with sumps and stripping lines and I treat with Grotamar Biocide, each year we strip out and eg cup full of water from each tank.

 

[dustywings]

My previous boat, a Riva 38, had stainless tanks which were 40 years old and were still perfect.

 

[volvopaul]

Not true, mine were marine alloy ok 28 yr s old but still corroded, and what about corrosion of alloy boats? if the conditions are right most metals will corrode.

Stray currents will use your tank as an anode , alloy ones especially.