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Primer inside a fuel tank!?

Wing nut

Member
A friend bought older RV6 partially built kit. He recently completed one fuel tank and went to start the other and noticed the parts were all primed except the skins. Of course he’s wondering why the heck he didn’t notice it before building the first tank. It looks like it is the Sherwin Williams wash primer. His question to me was “do you think the primer in the tank is a problem?” Gosh I really don’t know I said. That’s a good question for this forum.
He’s ready to rip the first tank apart and re do it but would appreciate thoughts and input you may have. Thanks
 
Chances are it's fine, but there's no way to know for sure. I have worked on many certified aircraft with primer on the inside of the fuel tanks that did nothing, but who knows what kind of primer the previous builder used.

What you could do is fill the tank partially with fuel and leave it for a few weeks to see what happens. Drain the fuel and if the fuel looks clean and the primer hasn't softened up, I wouldn't worry about it.
 
Slosh?

I’ve seen a pair of tanks that had sloshing compound that looked like zinc chromate. It felt a bit soft under a thumbnail, not a all like chromate primer. Not that sloshing is a great idea, but at least it’s not primer. I’d go with xcape’s idea of putting fuel in and seeing what happens. BTW, there is an old Vans Service Bulletin about sloshing compound bubbling and separating from the insides of fuel tanks. (and that’s what was happening to the afore mentioned tanks) Even if it’s doing that, all is not lost. Weep No More can still save the tank... for a price.
 
Vans sell a fuel tank repair kit which allows round access holes to be cut in the rear baffle so as to get inside the tank without major disassembly, then patched. This may be an option for cleaning off the primer in the completed tank, if that is what your friends decides to do.
 
If it is good epoxy primer it is OK. What is less desirable is the slosh compound that was recommended back in the day by Van's. It is a tank sealant, long been out of favor. It was white. Primer, if quality epoxy primer it will be fine with Av gas. Even if a little dissolves it it not going to cause an issue. If it was poorly done and flakes off then that might bock to filter. Monitor to fuel filters.

There is no PHOTO... so this is a qualified answer and you accept all risk. (Disclaimer required by my lawyer at Dewey Cheatem and Howe. Cheers)
 
P60G2

Probably no help but I have learned to keep Alumiprep far away from SW P60G2. Peels the stuff off like paint remover. Not sure why but I think it's some sort of chemical reaction.
Just an idea if it is SW Wash Primer P60G2.
 
No way I'd fly with tanks like that! :) The aluminum is aggressively roughened for tooth adhesion, cleaned with acetone to remove oils that improves adhesion, then liberally lathered with proseal for sealing and adhesion. Primer is an unwanted and undesirable feature to add to the stackup- off label as they say. I usually answer questions about doing tough jobs by asking myself: "When the tanks start leaking in the future, what would I have been willing to do now?". Buy the proseal remover at Aircraft Spruce , drill out the rivets, clean everything up, and do the job right- you'll feel much better when it's done.
 
No way I'd fly with tanks like that! :) The aluminum is aggressively roughened for tooth adhesion, cleaned with acetone to remove oils that improves adhesion, then liberally lathered with proseal for sealing and adhesion. Primer is an unwanted and undesirable feature to add to the stackup- off label as they say. I usually answer questions about doing tough jobs by asking myself: "When the tanks start leaking in the future, what would I have been willing to do now?". Buy the proseal remover at Aircraft Spruce , drill out the rivets, clean everything up, and do the job right- you'll feel much better when it's done.

That's a little much to say. Most certified aircraft have primer inside the tanks. From airliners to skyhawks and when applied correctly works just fine.

Primer is literally made to adhere to surfaces and promote adhesion. The new builder needs to do his due diligence but there is a very real possibility he does not need to strip and rebuild his tanks.
 
I am a stickler for having the job done right, especially when it comes to the safety of the aircraft. If it were me, I would purchase all of the components required to make a new fuel tank and replace it.
 
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