Pro's & Con's of Corrosion Painting

[johnb]

I am looking into purchasing a RV-12 kit. I am leaning to corrosion painting but because of the limited emtpy weight parameters, I need some input from builders that have and have not corrosive painted their airplane. Any input will welcomed and helpful. (I know that painting the airplane will add about 20 pounds to the weight.)

Thanks and regards
john bryan
677663

[rleffler]

You are bringing up a religious discussion.

If you live near the coast where salt and/or humidity levels may be high, prime.

If you lose sleep or worry about corrosion, prime.

If you lose sleep or worry about weight, don't prime.

The is no right answer. What makes you happy is all that matters.

I did prime my RV-10. I had corrosion issues in my Cherokee and didn't want to go through that again in the RV.

[Kyle Boatright]

I don't know about the -12, but on the earlier models, Van's specified "these parts" need priming. Essentially, they recommended you prime any extruded angle or anything else that wasn't alclad.

I completely primed the interior of my RV-6, but if I was gonna do it again, I'd just zinc chromate prime the non-alclad items and the faying surfaces on the other parts. I live in North Georgia, and my airplane is hangared, so corrosion isn't a big worry of mine.

[WLIU]

I will note that many Pipers were built "inexpensively", so are more prone to corrosion. RV's use a lot of alclad and so won't have the same problems. I will suggest that you should prime all of the steel parts and the parts that Van's specifically says need protection, and call it good. And I am sure that a telephone call to the factory will get you some good advice.

Weight is the enemy in airplanes. The challenge is to make good decisions about where to add ounces and where not to. Ounces add up into pounds so if you want good performance you look at every ounce and ask whether it is necessary, which is what you are doing.

Best of luck,

Wes
N78PS

[Eric Witherspoon]

Another aspect to the question - is the RV-12 primarily 6061, or did Van's stick with their traditional 2024 Alclad? There are those who believe that with 2024 Alclad, if every last possible surface isn't epoxy primed, the entire aircraft turns to dust the instant there's daylight beneath the tires. A lot of the lower/slower LSA's are being built from 6061, which is what a lot of boats are made of. It's more inherently corrosion resistant than 2024. How much more? Like someone else said, it depends on your operating / storage envrionment and personal beliefs.

[prasmussen]

Thought the pure aluminum coating was supposed to overcome the tendency of the copper alloy to corrode; that the Alclad was, in fact, one of the materials we were to look for? Somebody a metallurgist?

[steveinindy]

Thought the pure aluminum coating was supposed to overcome the tendency of the copper alloy to corrode; that the Alclad was, in fact, one of the materials we were to look for? Somebody a metallurgist?

The issue- at least as I understand it, with my limited knowledge of metallurgy- are the things we do with the metal (drill, grind, sand, bend, scratch, etc) which may overcome the protection of the alclad finish.

[Auburntsts]

Ahhh, nothing like a good primer discussion. Since you asked, I did a combination. I completely primed my tailcone and emp using the following process:

1. Clean parts (I used Dawn dishwashing detergent to remove oils)
2. Etch parts (scrubbed parts with maroon scotchbrite and alumiprep (aka phosphoric acid))
3. Alodine parts
4. Prime with epoxy primer (I used Stewart Systems water based primer sealer). If you do prime, take a good look at your primer of choice because some are porous and designed to be top coated which bascially defeats the purpose of corrision protection

All of that's a lot of work. For my wings I did all of that for just the ribs and primed only the rivet lines on the skins, For my fuse, I dropped priming altogether except for spots where I scratched the ALCLAD. For that I used rattle can primer.

Personally, if I had to do it all over again I'd only spot prime scratches and the parts Van's specifically calls out to be primed and call it good even if lived on the coast. YMMV.....

As for 2024 vs 6061, the 6061-T6 used in the RV-10 is not corrosion treated and must be primed. My assumption, knowing Van's penchant for keeping costs down, is the same materials are used in the RV-12, but I don't know for sure.

[Bob H]

The RV-12 uses clad 2024-T3 sheet. Cladding provides good corrosion resistance as long as you don't live in salt environment. Previous advice on spot priming faying joints is good one and areas with penetrations where hole surfaces can see moisture. Another method for riveted holes is to coat rivet with zinc chromate before upsetting so hole surface sees the coating ( wet installation).
I'm in dry western mountain climate and a friend's RV with no priming has no issues.

[johnb]

I want to thank all that have replied to my topic. I will take into account everything mentioned here in helping me make a decision on corrosive painting my aircraft. I live in a humid environment so I am leaning to corrosive painting my aircraft but have not made a final decision. Again thank you all.

regards
john
677663