Question about priming tank parts...

Gregg Brightwell · #1 09-24-2013, 04:28 PM

....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

wirejock · #2 09-24-2013, 05:13 PM

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.

blueflyer · #3 09-24-2013, 05:15 PM

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 · #4 09-24-2013, 05:16 PM

Nothing in the fuel tanks... just a very bad idea.

az_gila · #5 09-24-2013, 06:27 PM

Quote:

Originally Posted by LifeofReiley

Nothing in the fuel tanks... just a very bad idea.

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.

PIN 37 · #6 09-24-2013, 06:30 PM

Quote:

Nothing in the fuel tanks... just a very bad idea.

Fuel is a good thing to have in there.

Sorry, coudn't resist that.

N941WR · #7 09-24-2013, 06:36 PM

Quote:

Originally Posted by PIN 37

Fuel is a good thing to have in there...

Unless you are on fire.

Sorry, coudn't resist that.

Scott Hersha · #8 09-24-2013, 07:06 PM

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.

Randle · #9 09-24-2013, 08:01 PM

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.

Gregg Brightwell · #10 09-24-2013, 08:51 PM

...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.