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  #11  
Old 02-10-2017, 01:27 PM
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ppilotmike ppilotmike is offline
 
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I'm a fairly young guy, building an RV-10, and I decided to only prime the parts Vans tells you to in the instructions. Basically, if it was AlClad protected from the factory, I didn't prime it. I've heard too many stories about GA aircraft that looked shiny and new inside after decades of use. I have no regrets, but I'm not flying yet either.. Worst case, I'll treat it later with Corrosion X.
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  #12  
Old 02-10-2017, 01:53 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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On this second plane I'm building, I'm not in the prime/no-prime camp.

Some parts I will. Some parts I won't.

I didn't prime, for example, the trim pieces on the RV-12 nor the Vertical stab.

Why?

I'm so impressed with how Van's engineers have eliminated weight on this kit that I think it's counterproductive to add it back, no matter how small.

And those particular parts can be rebuilt in an afternoon for a few bucks if it came to corrosion, which it probably won't.

And any part that actually is directly exposed to the elements is primed.

Rattle cans for me.
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  #13  
Old 02-10-2017, 02:31 PM
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I'm in Mike Rettig's camp. Shiny aluminum except in a few places. The painter did prime prior to painting the outside, but that's his business.

John
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  #14  
Old 02-10-2017, 03:17 PM
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There is no coating, treatment, or process that will prevent corrosion. There are different levels of protection, but nothing makes 2024 corrosion proof.

Alclad is a conversion process which changes the alloy surface to a more pure state which is a lot more corrosion resistant than the base alloy.
Zinc Chromate is a sacrificial coating and toxic deterrent to organic growth. The coating will corrode once the top coat has been compromised and as long as there is still chromate that is unspent, it will protect the base material. However, once the chromate is depleted, corrosion will take its next victim.
Two part epoxies encapsulate the base metal so moisture can not penetrate and set up the necessary electrolysis for corrosion to start.
Corrosion X is a soup of compounds that deposit as a thin film of protection and requires retreatment in many environments.

The level of protection needed to keep corrosion at bay has everything to do with the environment and exposure to water, salt, and other corrosion accelerators. Choose the level of protection that you feel will meet your needs or as some have done, for resell.

I know this didn't answer the question, but there isn't one easy answer, or a silver bullet that can completely eliminate the possibility of corrosion. My current projects skins where anodized, then zinc chronate primed, then top coated. They still corroded due to time, environment, and neglect.

If anybody has regrets about not priming, it would be someone who's airplane was in an environment that had the potential to promote corrosion. Kind of stating the obvious. Someone without regret hasn't been in that same environment.
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  #15  
Old 02-11-2017, 05:54 AM
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Bill Boyd Bill Boyd is offline
 
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Default Yeah, it depends.

My project came to me in the canoe/almost-a-quick-build stage, and had been extensively interior-primed with AKZO. It's destined to make a lot of trips to the Carolina coast where it will sit unhangared for days at a time within earshot of the surf. So as I moved forward, I primed the remaining pieces with self-etching single part rattle can primer, mostly on the fay and inaccessible underside surfaces. Anything completely removable and interior, such as seat backs, was left natural on all sides, except the fay surfaces between components. Just too easy to remove and replace if ever needed, and not a structural issue even if corrosion were to start there, as an example.

No point adding totally unnecessary weight; it does add up. As does cost.
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  #16  
Old 02-11-2017, 10:35 AM
rongawer rongawer is offline
 
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Quote:
Originally Posted by JonJay View Post
There is no coating, treatment, or process that will prevent corrosion. There are different levels of protection, but nothing makes 2024 corrosion proof.
Ok, so I agree with your sentiment, but I disagree that corrosion can't be prevented. It can, it's just a matter of how serious you want to get about it and the money you want to spend.

Corrosion is simply an electrical process of oxygen reduction. If you inhibit the voltage potential or create a barrier for oxygen access, you will stop corrosion. And there are ways to prevent corrosion. One is to create a permanent barrier; such as marine coatings used by the Navy such as a DEVRAN 200 series coating, which adheres in ways that defy logic and is impervious to any oxygen penetration, however even it starts to break down above 230ºF. Of course, you need a governmental budget to afford it.

The other way is to provide cathodic protection, which in the case of CorrosionX, is the provision of a "sacrificial anode" chemical, which more readily gives up electrons to the reduction process than the material being protected; in this case, aluminum.

If you're really serious about it (such as if you keep your airplane next to a beach in Florida), you can go with the "belt and suspenders" approach of priming with a sacrificial anode type primer (zinc chromate is one) and then spray with a corrosion inhibitor on biannual basis, such as Corrosion X. Or you can just say "screw it, it'll be good for the rest of my flying career" and forget about any protection knowing the plane will need either a lot of help or the scrap yard many years later.
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  #17  
Old 02-11-2017, 10:21 PM
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MartinACFactory MartinACFactory is offline
 
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Default Maybe I have OCD Syndrome...

Reading through the various post on this thread makes me feel like maybe amongst the common RV builders, I could be a wacko, a over the top perfectionist or worst I have incurable major OCD syndrome ....

In the ever lasting debate about to be a primer or not to be a primer, I chose to be a primer, with no exception to the rule.... Why? Because

1) I make no compromise on the quality of my build, despite the sometime higher cost and slightly increase weight.
2) This is what I have been taught to do in Aircraft Manufacturing School, and subsequently working on the Aircraft Manufacturing Industry.
3) I will fly and operate my RV in an environment where you just look at some thing, and it corrodes, especially in our cold & humid snowy Eastern Canada Winter.
4) I want my aircraft to last and outlast me
5) If I ever sell my aircraft, I want the future owner to have full confidence on the quality of my build.

That all said, picture below is yesterday evening and today all day production....RV parts that have been scuffed, then subsequently dipped in Alumprep 33 and Alodine 1201 baths. These parts will be primed with Sherwin William Green Zinc Chromate epoxy primer at a local bodyshop on Monday morning



RV Experts will recognize RV-8 fuselage parts I just love to turn aluminum RV parts into gold

Do I regret priming my RV-8 ? Obviously not ! What I regret though is that it takes me an awful lot of time to do it. For the next RV someday, for sure I will work on a "lean manufacturing process" to make this faster....
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  #18  
Old 04-28-2017, 07:51 AM
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bkervaski bkervaski is offline
 
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I'm in the "keep it simple" camp and only prime parts exposed or what Van's indicates in the instructions .. however .. I have a question that came up last night during my build:

If Alclad is a surface process, and a lot of the parts from vans require trimming and cutting, aren't those areas that are trimmed and cut (or accidentally scuffed) no longer Alclad? Does anyone that has not primed see corrosion on the edge of ribs, etc, over time?
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  #19  
Old 04-28-2017, 09:01 AM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by bkervaski View Post
I'm in the "keep it simple" camp and only prime parts exposed or what Van's indicates in the instructions .. however .. I have a question that came up last night during my build:

If Alclad is a surface process, and a lot of the parts from vans require trimming and cutting, aren't those areas that are trimmed and cut (or accidentally scuffed) no longer Alclad? Does anyone that has not primed see corrosion on the edge of ribs, etc, over time?
Haven't seen any evidence of edge corrosion on unprimed Alclad in my hangared 1999 RV-6. However, those components are located in the interior of the plane and protected from outside exposure.
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Last edited by Sam Buchanan : 04-28-2017 at 09:06 AM.
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  #20  
Old 04-28-2017, 09:27 AM
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kentlik kentlik is offline
 
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Quote:
Originally Posted by rv7boy View Post
My 1969 C172 had the CorrosionX treatment a couple of years ago due to very light corrosion from wing root insulation that got wet during a storm at Oshkosh. If it had not gotten wet I'm convinced it STILL would be corrosion free. In the build of my RV7, I'm not priming the Alclad. I'm 68 years old. If I finish my RV in a couple of years, I figure I should be about 116 years old before I start worrying about corrosion.
My thoughts exactly!
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