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Question about priming tank parts...

Gregg Brightwell

Gregg Brightwell

Well Known Member
....Please do not flame me if this is truly a stupid question. In my past life as an Experimental A&P, Flight Mechanic, and Avionics guy, I have seen deep inside many airplanes. My question is, have any of you primed the inside parts of your fuel tanks? A search on this issue shows a lot of shiny non primered metal in the tank construction photos. Yet certified aircraft I have seen have have the green zinc chromate primer INSIDE the tank. I am starting my tanks, and would like to primer, but obviously don't want avgas dissolving my primer. (Using a 2 part Valspar epoxy primer)

No rock throwing please.....
GB
 
priming tank

I'm close to that stage as well. The consensus from those asked is no. I am working on ribs and scotch brite only the areas where proseal will touch. I suppose if there is water in the tank, it could corrode but that much water would probably be noticed and a bigger problem anyway. :D
 
me too

Gregg, very timely post. I just primed all my ribs with rattle can duplicolor self etching primer. Kinda did all of them before I thought about these ribs being exposed to fuel. So.....I am very interested in the responses to your question as well.

 
LifeofReiley said:
Nothing in the fuel tanks... just a very bad idea.
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Well not exactly....

Alodine is acceptable inside the fuel tanks and will actually slightly improve the adhesion of Proseal, according to the Mil Spec.

However, most builders just clean, and perhaps acid etch, at the Proseal joints in the tanks.
 
The RV14 builders manual definitely says "do not prime internal fuel tank parts". Other than alodine as Gil says - which isn't primer - nothing should be done except thorough cleaning. I scotchbrighted all faying surfaces to ensure good pro-seal adhesion prior to cleaning and assembly.
 
I work on certifieds and can tell you they are still primed internally, in fact, I was just inside the wing tank of a very large cargo yesterday. I definitely will not say don't prime them, but you must think of the reason they are primed as well as the reasons they aren't. The 2 part primer you are debating on using will not dissolve when in contact with the fuel. Many of the certifieds that are primed is to protect the large areas from the corrosion during the times the aircraft tanks are not filled for extended periods, and to protect the metals due to the dissimilarities of the materials to include the vast available fuel types, from Jet A to JP8. Do I think its needed in our applications, no. Would it hurt, have to say no to that as well except by a weight and time standpoint.
 
Well, guess it wasn't a stupid question...

...after all. Majority of ye say nay. I WILL alodine rib flanges and skin rivet lines.
I will take as much info as I can get. Time to get these wings DONE. I have a leading edge skin, 4 bottom skins, and 2 single piece top skins to prime. That is a LOT of scotch briting! Was going to prime tank skins, but now just the outside, and alodine inside.
 
Gregg Brightwell said:
I have a leading edge skin, 4 bottom skins, and 2 single piece top skins to prime. That is a LOT of scotch briting!
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Use a vibrating sander over the top of grey scotch bright. You do not need to attach the Scotch Bright to the sander. Just cut a piece of Scotch Bright a little bigger than the sander pad, set the sander over the pad, and scuff away. This will make very short work of scuffing your sheets and it does a good job.

I wouldn't even consider priming inside the tank. Remember, all those folks that sloshed their tanks 25 years ago thought it was a good idea. Not so much after it starts coming off.
 
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blueflyer said:
Gregg, very timely post. I just primed all my ribs with rattle can duplicolor self etching primer. Kinda did all of them before I thought about these ribs being exposed to fuel. So.....I am very interested in the responses to your question as well.

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Hate to be the bearer of bad news, but I would highly doubt that this is compatible with fuel. My recommendation would be to get expert confirmation that it is OK before even thinking about flying the plane with primed internal tank ribs!
 
I didn't prime any parts inside the fuel tank. I just consider an oil substance to be good corrosion protection, BUT I also have a weird habit of keeping my tanks full to lessen the chance of condensation etc.
 
Yeah, definately get the duplicolor primer off the internal tank parts. I have used that primer quite a bit and it is not in any way compatable or resistant to fuel. It will be easy to remove, just wipe it off with some acetone or MEK. Heck, 90% rubbing alcohol will take it off also.
 
got it.

thanks for the advice. I'll get them cleaned up.

WingsOnWheels said:
Yeah, definately get the duplicolor primer off the internal tank parts. I have used that primer quite a bit and it is not in any way compatable or resistant to fuel. It will be easy to remove, just wipe it off with some acetone or MEK. Heck, 90% rubbing alcohol will take it off also.
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Randle said:
I work on certifieds and can tell you they are still primed internally, in fact, I was just inside the wing tank of a very large cargo yesterday. I definitely will not say don't prime them, but you must think of the reason they are primed as well as the reasons they aren't. The 2 part primer you are debating on using will not dissolve when in contact with the fuel. Many of the certifieds that are primed is to protect the large areas from the corrosion during the times the aircraft tanks are not filled for extended periods, and to protect the metals due to the dissimilarities of the materials to include the vast available fuel types, from Jet A to JP8. Do I think its needed in our applications, no. Would it hurt, have to say no to that as well except by a weight and time standpoint.
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The tanks on my 59 year old Cessna 170 are un-primed and un-alodined, and are just as shiny on the inside as the day they were made. I would never apply primer or paint to the interior of a tank unless it was a product specficaly designed for the purpose and applied per manufacturers recommendation.

Alodine is a chemical conversion coating, and is chemically bonded to the metal as opposed to just being adhered to it. Fuel is NOT going to make it turn loose. It's probably a good idea if you plan on running ethanol-laced fuel ( I don't), but there are enough bare alclad tanks in the RV world that I didn't think it worth the effort.
 
I'm just finishing up the tanks and am looking at priming the outside however I know even a tough three part epoxy primer won't adhere to tank sealant, at least not long term. I'm less than 20 mi from the south Texas coast line and want maximum protection. With fully cured tank sealant, will epoxy primer degrade the tank sealant? Again this is only on the exterior of the tank. I have to agree that anything other than sealant on the inside is a bad idea. Even the construction manual discourages priming the inside tank parts.
 
WingsOnWheels said:
Yeah, definately get the duplicolor primer off the internal tank parts. I have used that primer quite a bit and it is not in any way compatable or resistant to fuel. It will be easy to remove, just wipe it off with some acetone or MEK. Heck, 90% rubbing alcohol will take it off also.
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Got em all cleaned up and back on track. thanks fellas. that could have caused me some trouble down the road.

 
priming outside finished tanks over proseal

I have kind of the oppisite question.... I did not prime anything yet but I have both end ribs prosealed and fittings in place. Can I spray my Akzo Nobel primer over the small parts of proseal on the parts squeezing in between ribs? Any recommendations will be appreciative:)

John
 
Primer

jerseypilot83 said:
I have kind of the oppisite question.... I did not prime anything yet but I have both end ribs prosealed and fittings in place. Can I spray my Akzo Nobel primer over the small parts of proseal on the parts squeezing in between ribs? Any recommendations will be appreciative:)

John
Click to expand...

I assume you're wondering if the primer will stick to proseal. Yes.
 
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