Aluminium Fuel Tanks: to paint or not to paint?

joliette

joliette

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The twin aluminium fuel tanks for my Levi Settimo Velo (http://www.facebook.com/#!/group.php?gid=179427293999) will be arriving soon. I plan to mount them on wooden chocks covered with hard neoprene and hold them down with aluminium straps with hard neoprene under them. This will allow air to circulate around the tanks which will kept dry beneath a fixed cockpit floor.

I am thinking about painting the tanks to help prevent corossion, but there seem to be different schools of thought on this issue. Also, the fuel fillers (bronze) and tanks will be electrically bonded together and to earth - for static spark prevention - by wiring them to an anode.

I have read that a protective oxide layer forms on bare aluminium and will provide protection againt corossion if not scratched. Is this correct or is it better to protect the tank with a paint system? If so, what paint system would you recommend?
 
Fairline never paint their ali tanks and on my last but one boat they looked lovely and shiny when 6 years old just as when the boat was new. They never saw any seawater

Ali does form an oxide layer that stops further oxidation and further corrosion in mild non galvanic conditions

So I would have thought no need to paint them if they are nearly always dry
 
I have twin 150 tanks made from aluminium sheet, each tank sits on a sheet of epoxy coated and painted ply with a layer of insertion rubber under them.

They fit under the cockpit seats on each side of the catamarans cockpit, the only access is is to the outside edge of each tank in the engine room/s, so I added a collection sump to each and all tubing is welded externally, also an alloy angle runs the full length on both sides, this bolted to the ply and the ply is bolted to reinforced sections of the hull.

Both tanks were never painted and have never had a problem after several years.

If you do not have a sump on your new tanks, it's not too late to add them.

Good luck.
 
Painting Tanks

I would recommend that you paint them if you can see them, a nice tidy painted tank area always looks good. You don't really have to paint them for longevity as long as they don't sit in salt water. As you say, (and I probably posted it), the ally forms a slightly white layer which is an oxide that stops any further corrosion. Sit them on open cell foam rubber, strap them with stainless straps with rubber inserts under to stop any galvanic reaction. MAke sure that they are well earthed.
We make most of the Fairline tanks so its good to know that they are still looking good. We are only now replacing 20+ year old tanks that we made.
P.S Why didn't you order the tanks from me !!
 
Special Tank

Hi, yes its made, not quite delivered yet due to various issues ...
Its a really nice tank, quite proud of it myself actually, even though we make about 1,000 a year.
Hope that it lasts you for many years !
SIMON
 
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jfm said:
Fairline never paint their ali tanks and on my last but one boat they looked lovely and shiny when 6 years old just as when the boat was new. They never saw any seawater

Ali does form an oxide layer that stops further oxidation and further corrosion in mild non galvanic conditions

So I would have thought no need to paint them if they are nearly always dry
Click to expand...

Department of Transport had a technical paper on the subject gong back to the days when they laid down specs for snow ploughs and gritters. Cannot find it now, however the general instruction for fabricated alloy tanks was to leave unpainted. Only alloy castings were to be treated and that was with a special rubber based paint.

Main objection to painting is that it excludes air, corrosion goes on without protection of oxide barrier.

In U.S. alloy tanks are rightly considered superior to stainless. Engine bed fabrication in heavy gauge alloy is also common practice, again unpainted.
 
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Latestarter1 said:
Department of Transport had a technical paper on the subject gong back to the days when they laid down specs for snow ploughs and gritters. Cannot find it now, however the general instruction for fabricated alloy tanks was to leave unpained. Only alloy castings were to be treated and that was with a special rubber based paint.

Main objection to painting is that it excludes air, corrosion goes on without protection of oxide barrier.

In U.S. alloy tanks are rightly considered superior to stainless. Engine bed fabrication in heavy gauge alloy is also common practice, again unpainted.
Click to expand...

Totally agree with you there Latestarter. Its really down to the grade of ally as well. Good marine grades will oxidise and then stabalize as long as they stay dry. Constant washing off knocks off the oxide and hence protection, having said that an occasional wipe with fresh water does no harm.
 
One simple solution is to lacquer them with a clear lacquer, then the best of both worlds, protection and visibility.
 
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