Fresh frame painting? alum stringer painting?

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Scottiniowa

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Nov 29, 2021
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Clarksville, Iowa
What are folks finding working best for a fresh airframe (media blasted to bare metal) as well as alum stringer painting. I find to many that feel a simple priming of alum parts is good enough (no top coat) And some feel that is true for the frame as well. I intend to have both top coated in as durable of material that I can apply, not going to go into the powder coat option as, I am not going to take this down the road, newly blasted in the winter (northern climate) The options are huge it would seem, but my glue will be stewart systems for the fabric, paint for everything not yet decided.

For clarification sake this frame is as large as any super cub, and stringers done is a similar fashion.

A rattle can solution would be nice, but certainly understand if this is deemed not workable. Open to all ideas, if they are backed up by experience, won't be risking the job on, " I think, perhaps, maybe, I have heard" opinions

thanks for your considerations on this, and if a thread has completely covered this, please point me in that direction.
 

rv7charlie

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If you're asking about 4130, I've got a sheet that came into my possession around 1990, and was probably 10 years old then. It's been stored in various high humidity (but covered) locations for as long as I've owned it. It was primed on one side with zinc chromate. The chromated side still looks pretty good. Zinc chromate works well on aluminum, too. Your call on whether using chromates concerns you (don't ignore the cautions; just evaluate them intelligently). You can still buy it in most states, but you might have to hunt for it. I know that it's been available in rattle cans in the past; that's what I've used. FWIW, if ;you can set up for one big spray session, it might be cheaper to buy a quart or two & spray it with that cheap Harbor Freight gun & just pitch the gun. It could take a lot of rattle cans to prime a whole project. I sprayed an entire Kolb project in latex with one of those $10 guns, and it turned out pretty well.

I can't tell you about what primers/finishes the Stewart stuff will attack (though I'd be surprised if it attacks zinc chromate), but the older dope based stuff seems to attack almost everything short of epoxy.
 

TFF

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Even if using Stewarts, the only thing I would paint 4130 is the polyfiber or Ceconite tube primer. It is not transparent to the atmosphere. They call it a primer but it is what they call a hard shell epoxy. There are mil spec and others out there. Auto primer is transparent. Even if it says epoxy. It will rust in time. It might not matter for the lifespan. Also if prepared correctly, it’s not chipping of without chipping in it. Other stuff might release in years time. To me it’s not worth it. Stewart’s has their own waterborne version. Some don’t like the idea of spraying water on something you are trying to protect drone it. Stringers, you could hit it with the primer. I think alodine would be lighter.
 

BBerson

Light Plane Philosopher
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I used water based acrylic on a painted steel file cabinet. It leached under the paint, rusted and looked terrible.
The best for steel tube is a light coat of Zinc spray. Comes in a spray can of zinc powder (grey). Then several coats of green or yellow zinc chromate primer to protect the soft grey zinc base. Then two coats of epoxy top coat.
 

Pops

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Best I have found is Poly-Fiber epoxy primer for the 4130. Picture of the PF epoxy primer on the LG of the SSSC. Next is Dupont Vari-Prime at your Dupont auto paint store.

I primed my 1981 Chevy 3/4 ton Chevy truck with Poly-Fiber epoxy primer then painted with Randthane Polar gray. I used what I had.
 

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