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S&S Swan Maintenance - Fuel Tank corrosion
22 December 2015 - 21:38
Join Date: 19 October 2012
Posts: 44

Fuel Tank corrosion
Dear Members,
i wish to share with you my last experience in fuel tank corrosion.

During my last autumn cruise of around 200nm I have discovered with great surprise that I was loosing diesel from the fuel tank!
While in harbour I got off the fuel tank. On the lower side I found many corrosions, I think is a galvanic corrosion (see pics). Someone can confirm it?

I must point out that just 30 days before the fuel tank was not like that (we got it off to wash it inside).
Then before starting my cruise I decided to install an electrical floating fuel indicator.
Can it be possible such very small electrical absorption could caused that kind of corrosion in just 30days?
It's also true true that until I've landed the fuel tank, I would have never been able to verify that the bilge under the fuel tank is the lowest part in the 44's. This means that the lower side of the fuel tank is always in touch with sea water.

Now while we were welding a new inox lower side of the fuel tank, I modified, extending the bilge pump tubes, in order to suck completely the bilge floor under the fuel tank.
Someone else have done the same experience?



detail of the corrosion

26 December 2015 - 08:36
Join Date: 02 January 2008
Posts: 1547

Dear Alberto
Electrical leaks can cause rapid corrosion on metals in water, and it is obvious that the new fuel gauge is the reason.
Is the gauge touching the tank wall inside in the corroded area? Diesel oil is not a good electrical conductor, and it is likely that there is contact. The gauge needs to be completely isolated.
Wishing you a Happy New Year

27 December 2015 - 16:27
Join Date: 19 October 2012
Posts: 44

Thanks Lars for your reply.
I have eliminated the gauge to avoid any electrical leaks.

Moreover i have extended the automatic bilge pumps pipe in order to suck sea water even under the thank...the lowest bilge on the 44's!


27 December 2015 - 17:21
Join Date: 29 January 2007
Posts: 913

Dear Alberto,

just be sure the automatic bilge pump will be connected directly to the battery, so when the boat is unattended and main battery switched off it works

Fair winds!

matteo (47/069 Vanessa)

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