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Bevan

Well Known Member
Is there any reason to alodine (interior and exterior) of the aluminum tube fuel lines especially if you want use auto fuel (possible water content) in the future? Will the alodined surface wear away eventually with the fuel flow? Will the alodine make the tube brittle and more susceptible to cracking? Other?

I found nothing in the archives.

Bevan
 
Bevan said:
Is there any reason to alodine (interior and exterior) of the aluminum tube fuel lines especially if you want use auto fuel (possible water content) in the future? Will the alodined surface wear away eventually with the fuel flow? Will the alodine make the tube brittle and more susceptible to cracking? Other?

I found nothing in the archives.

Bevan
Click to expand...

i do not think this is necessary... running auto fuel should not be a problem if there is water content... its not like its exposed to oxygen and water is just sitting there... just my .02
 
No, there is no reason to alodine the outside and you should definitely not alodine the inside, fuel and chromates do not go well together. Fuel pipe is usually made from 5005 or 5052 Al alloy, both have reasonably good corrosion resistance so no further protection is necessary. You should not alodine the inside of your tanks, either.

For reference Alodine does not make aluminum alloy brittle or susceptible to cracking - are you thinking of anodizing?

Pete
 
No treatment then?

I was thinking that since the aluminum tube is not alclad (or protected in any other way other than the characteristics of it's alloy), it would benefit by some type of protection. Soaking the tubing (after bending etc) in alodine would be the easiest way. It would seem so far that this not required nor standard practice although the fittings are nicely anodized.

Bevan
 
But all aluminum alloy is not made equal. 2024 needs the cladding to stop it disolving away before your 2nd annual, but 3003, 5005 or even 5052 does not need that protection because of the different alloying elements.

Pure aluminum (1100) does not need any protection, but is soft - add 4% copper (2024) and it is now a useful structural alloy, but corrodes. Add manganese instead of copper (3003) and there is some strength improvement over pure Al (20%) with little loss of corrosion resistance. Add magnesium rather than manganese (5005) and the alloy stands up in service better. 5052 has a few other minor alloying elements (such as silicon and iron, and chromium) but still has similar properties of good corrosion resistance, particularly in a marine environment, good workability (you can bend the tube without it crimping or cracking) and reasonable strength.

Fittings are anodized to identify the material they are made from as much as for corrosion protection. If you feel the need to alodine the outside of your fuel pipes, then go ahead. There is no need to do it, but no real penalty other than the time it takes. I would advise against alodining the inside of the fuel pipes as a strontium chromate primer is really required to withstand the fuel, and that is not generally available.

Pete
 
Actually...

penguin said:
..... I would advise against alodining the inside of the fuel pipes as a strontium chromate primer is really required to withstand the fuel, and that is not generally available.

Pete
Click to expand...

...the fuel sealer Mil-Spec even lists peel strength on an alodined surface.
Alodining the interior of fuel tanks is acceptable, but not really needed, as you say - but it's not bad...:)

Also, the 463-12-8 Akzo epoxy primer for Spruce is 7%-12 % Strontium Chromate by it's MSDS, and is generally available -lots of us already use it...:)
 
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