Prime and Paint

[at7000ft]

Plus, to make the case for no primer even stronger, I forgot to mention that unless it's a two part epoxy or some other high end primer, the off the shelf brands in rattle can are permeable. So, they aren't going to protect against corrosion except if you put a top coat on top of them. More expense, more time, and more weight.

I have asked the Monett's (of Sonex aircraft fame) about the need for interior priming, they agree that it's a waste of time. Sonex is also 6061.

[MikeS.]

IMO - The post above about spray can primers is not entirely correct. If a spray primer is "sandable" or has a flat finish then it is permeable to moisture and provides little long-term protection. However, if a spray can primer provides a gloss or semi-gloss finish it will provide as much moisture protection as a finished top coat that has the same texture. There are several spray primers that provide a gloss or semi-gloss finish and the Zinc Chromate spray can primers provide this protective barrier.

Having lived in a high humid zone all of my life, where most metal objects begin to show some form of corrosion very quickly, convinces me that my interior structure needs to be protected with Zinc Chromate. I'm not worried about the structure while I own my Panther, its the next person(s) that own it that I'm trying to protect. It's my reputation on the line, even after I'm dead and buried, and I'm going to protect it with an extra $200 worth of Zinc Chromate.

If your airframe will stay in the dry western climate all of its life then primer is a waste of time, money, and weight; but there are no guarantees that it will stay out there. Everyone has to decide whether saving 10-15 pounds is really going to make that much of a difference for their flying conditions, especially if building the LSA version with less horsepower. This is a single seat airplane and in my opinion the only variables that will really suffer are the amount of luggage that you can carry on a trip and if trying to fly out of a very short airstrip under high/hot conditions. Those two variables aren't a factor for my planned use of my Panther.

To each his own...

Mike

[Sacpilot]

Plus, to make the case for no primer even stronger, I forgot to mention that unless it's a two part epoxy or some other high end primer, the off the shelf brands in rattle can are permeable. So, they aren't going to protect against corrosion except if you put a top coat on top of them. More expense, more time, and more weight.

[Sacpilot]

I just completed Zenith 750 with 6061-t6 and avex rivets. I started by priming everything. Stopped toward the last 20 percent of build. Waste of time, money, and useful load.

After two years of building and countless hours of research on priming, Dan W. said it best on the phone yesterday, and it finally sank in. Vans 2025 is covered with AL .003" thick. Bc 2025 is really really prone to corrosion it has the coating. Scratch it, you need to prime it. The exposed surface in the scratch will corrode.

6061-t6 is the same alloy all the way through. No coating. If you scratch the surface, the exposed scratch is the same alloy. So, why would you choose to prime any given 6061 structure over another? Worse yet, why every internal structure? They are all the same alloy throughout! Bottom line, scratches only need to be removed for cracking issues. Deburred holes and deburred parts don't need to be primed either. Any aluminum surface will see some form of filliform corrosion over time (non destructive corrosion. It's the normal process of aluminum and oxygen combining to create a natural barrier of protection.)

As someone once said, why are we trying to make 60 year aircraft when you will fly it for another 15-30 years tops depending on age.

If an A and P, or engineer,wants to back up my assertion,that would be great

[PlaneDan]

Thanks to everyone for their responses. I think I am good to go now.

Tony,

I am just going to paint the interior of the aft fuselage back to and including the first bulkhead. I guess you would call that the baggage area. It would be nice to know a paint color that would match the powder coating of the main fuselage.

Thanks,

Dan

[MikeS.]

I am using PTI Zinc Chromate Primer in aerosol cans from AS. It's available in dark green or yellow. I chose yellow.

Scuff the area to be primed with Scotchbrite pad, wash the part with Dawn detergent and rinse well, dry, wipe part with MEK, Acetone, or Laquer Thinner, then spray primer.

http://www.aircraftspruce.com/catalog/c ... ckkey=7822
http://www.aircraftspruce.com/catalog/p ... mertds.pdf

Mike

[Tony Spicer]

Will someone help me out with this please. I could ask my RV friends, but it is built using alclad aluminum, where ours it built using 6061-T6, and I don't know if the materials or the process is the same.

Dan,

What exactly are you planning to paint? If it's the interior of the cage panels, the prototype was done with rattle cans and looks fine. And for the record, RV or Panther, prep and paint will be the same no matter which paint you choose to use.

Tony

[Renegade007]

I used to own an aircraft paint shop . There are several ways to pre aluminum for paint .. The traditional is an Aladine and Acid wash ... This etches chemically the aluminum and gives the paint and or primer a tooth to stick to. Zink Chromate is a great primer to use but do not sand after words if you can find it. It puts protective layer on it and seals it so that no corrosion can get under the paint and get started. Caution once you start this acid Aladine wash be ready to paint even the next day if left unprotected after the wash it will then start to corrode the aluminum.

A good product to use that does do both is called Aluma grip .. This can be used after aluminum prep as a primer and utilized the chemical etch in a one step manor. Then after flash a conventional paint can be applied.

Also using Poly Urethane paints especially one step paints are best used for Aircraft. This gives the best airtight coverage with least amount of layers of paint. It give s the base color with a shine instead of two stage paints where you put several layers of color on then get the shine with several layers of clear. All good makes of paint .. Imron, Dupont, PPG etc have good single stage poly Urethane paints.

I hope this helps

Doc Bailey

[PlaneDan]

Will someone help me out with this please. I could ask my RV friends, but it is built using alclad aluminum, where ours it built using 6061-T6, and I don't know if the materials or the process is the same.

[PlaneDan]

There are areas inside the fuselage that I wish to prime and paint as I build, where "prime if desired" is specified. I would like to use a grey paint, that may match closely the grey harness, assuming that grey got enough votes.

So, what preparation is necessary for priming? What primer product should be used? Is it available in a spray can, for convenience where small areas need to be primed? What paint should be used?

I am not priming nor painting where not necessary for aesthetics, to save weight and work and money. I have not previously built an aluminum plane, thus the reason for my questions.