Anyone have pictures of unprimed internal surfaces?

[ppilotmike]

..someone, who's opinion I value, told me that he has seen the inside of several very old planes (50+ years) that were "Al clad Only". He said they looked like the inside of a beer can, no corrosion whatsoever.

I agree, if corrosion was such an issue, it would seem that there would be more threads & pics about it. Perhaps the corrosion problems referred to are 1) something people don't care to share pictures of, 2) something people don't check for or know how to identify, or 3)something used mainly to sell corrosion prevention services/products.

To me, priming probably won't hurt, so if you want to do it, go for it. If you don't, well then, don't.

[Flying Canuck]

This may be a moot point in Canada. It's my understanding that priming interior surfaces is a requirement with the MD-RA. The pre-cover inspection document lists "Are all surfaces protected against environmental deterioration" as one of the questions to be checked by the inspector.

[Boomer506]

I agree that the time involved in a full clean, prep, etch, spray process for internal alclad parts is overkill. But a quick sponge brush on of Dupont Variprime 615S self etch primer has been a quick, easy and inexpensive solution for me. I was just uncomfortable with leaving things bare internally. But I didn't want to spend 5 years building my airplane and setting up a spray booth or spray hood every two days. So I will clean internal parts with a spray bottle of degreaser type cleaner, then mix a small batch of variprime 615s and mix it thin (about 2 to 1).



I then brush it on with a sponge brush, so thin that it flows out nicely, and dries within minutes. If there happens to be a finger print on the part, the metal etch primer cuts right through, so the parts don't have to be super clean. I can be riveting almost immediately. Faster if I use my heat gun.



This process also puts a thin primer between riveted parts, which makes me more comfortable knowing that water will be spending time there too. I used this process on my RV-6 and am doing it on my RV-8 as well. It just seems like a good middle ground between bare, and full on spray booth priming.

[XOverZero]

With a nod to ppilotmike?we share the same bottom line opinion.

Apart from major contributing factors such as storage or environment, the decision on whether to prime or not, or how much, comes down simply to what satisfies the builder. Pride of accomplishment is a major overriding motivator in homebuilding. So the real number one question is almost always, what do you WANT to do?

All the debate about unprimed aluminum airplanes that are a half-century old and still airworthy - still flying, are noted and appreciated. However, has there ever been any data to support the conclusion that priming is a wasted effort, as some claim? Many people have cited the fact that there are thousands of airplanes parked outside all over the world that are decades old, are not primed inside and are not corroded. Good. That?s all very true, but it isn?t data.

The question that arises, but which I have never heard voiced, is this: How many airplanes of the same age and history have long since gone to the scrap heap because they were shot through with corrosion? Is it in the thousands? Anybody counting those? No? If there were numbers to work with, the quantity of good and airworthy vs. bad and rotted, we could come up with probability figures?data. Lacking such data, the argument against priming by reference to the existing fleet is only anecdotal at best.

The bottom line is going to remain. It?s your airplane. What makes you happy?

[David Paule]

It all depends on location.

My 61 year old Cessna 180 has minimal internal corrosion since it has been primarily an inland airplane. It had none until I tied it down near Philadelphia for six months and then it picked up what it has now.

I learned to fly in Santa Monica, three miles or so from the ocean. The unprimed airplanes there, all much younger, had heavy to severe corrosion.

Location and intended usage determine priming needs.

I'm priming my RV-3B primarily for the benefit of the next owner. I don't expect that it will be necessary during my remaining lifetime. I'm using SEM rattle can primer, which is excellent, on the formed parts, and Moeller rattle can zinc chromate primer on the skins. The latter is not an excellent primer and I will try an alternate brand.

The SEM dries quickly and is tough. Its only corrosion protection is that of a barrier.

Dave

[Sam Buchanan]

Originally Posted by Tbutler

Sam, did you prime where ribs and skins touch? Like the above photo? Did you prime anything?? I have not so far, only sprayed rattle can primer on the few parts that the plans specifically call for, like the tank attach brackets, doubler plates, etc. Hoping this will work out fine in the end. I've read your blog and views on priming and feel the same. My goal is to fly and travel in the airplane, not still be building it. Nothing lasts forever....

-Travis

I sprayed wash primer on the ribs.....just because of "conventional wisdom" at the time. If building another RV, I wouldn't prime anything except extrusions.

[Lemmingman]

For me, I primed pretty much all the faying surfaces.

[Flying Canuck]

Originally Posted by Flying Canuck

This may be a moot point in Canada. It's my understanding that priming interior surfaces is a requirement with the MD-RA. The pre-cover inspection document lists "Are all surfaces protected against environmental deterioration" as one of the questions to be checked by the inspector.

Actually the more pertinent question during inspection asked is "Are all interiors treated for protection from environmental deterioration?"

[MarkW]

I previously shared a hanger with an A & P and IA who did a lot of annuals for certified aircraft of all sorts. 2 of 10 had corrosion. Maybe one of twenty were severe. I may have been outside storage that caused the problem. It sure was sad to see an airplane badly corroded and worth almost nothing.

[wirejock]

Originally Posted by Polar

I just spent the last two days prepping and priming all the internal surfaces on my empennage kit. Somewhere during all the scrubbing and rinsing and spraying I was thinking about the prime / don't prime debate. I've heard convincing arguments on both sides by people whose opinion I value, but I have yet to come across anyone who offers proof that priming isn't necessary. As in, I've never seen a picture of the inside surfaces of a vans aircraft with 'X' amount of hours. A control, if you will.

Not an interior surface but it is a valid test.
http://www.vansairforce.com/communit...2&postcount=12
I sprayed everything inside with it. Cabin parts were sprayed with Jet Flex SB within 30 minute window of P60G2.