Surfaces to prime?

[docjefft]

Hello! Hope everyone had a Merry Christmas and that the New Year will bring you many blessings! I am now just a month or so out from ordering my -10 empennage and have question about priming. I will NOT reopen the dreaded primer wars discussions of the past. I am already settled on the fact that I will prime and what agents I will use. However, I notice that there is a lot of discussion about priming internal surfaces, e.g. ribs, inner skins, etc., but not much about the exterior surfaces. My uncertainties are these:
1. When do outer surfaces get primed? I know some folks leave the blue plastic on the exterior skins (except where the rivets go) throughout the build. But some of the documents I've seen online say to remove the plastic asap.
2. If you do remove the plastic early on, how is the exposed aluminum protected? Just by the alclad properties? Won't some corrosion occur that will require extra prep before exterior paint is applied?
3. As a followup to #2, is it OK to leave exterior surfaces unprimed, either with or without blue plastic, until ready to prime and paint the exterior as construction of the plane nears completion? Would this also apply to the visible surfaces inside the cabin?
4. Is there a good reason not to prime exterior/visible surfaces early in construcion, e.g. why not prime the exterior empennage skins while priming their inner surfaces? It seems that the simplest thing to do would be to prime everything inside and out before assembling all the parts.

Just trying to prepare myself for the road ahead!

Thanks!
Jeff Trawick

[MED]

Van's recommends removing the blue plastic asap as it may become more difficult to remove with time, plus there is a potential for corrosion forming beneath the plastic. The alclad (pure aluminum coating) will prevent corrosion while in your shop environment. Pure aluminum forms a protective oxide layer that is very corrosion resistant, as long as moisture etc. is not held in contact with it. As for priming the exterior surfaces, there is a short time recommended between priming and application of topcoat, so priming months (or years) before you finally paint will mean the primer will need to be removed and reapplied or refreshed (weight) prior to applying the paint.

[wirejock]

Originally Posted by MED

Van's recommends removing the blue plastic asap as it may become more difficult to remove with time, plus there is a potential for corrosion forming beneath the plastic. The alclad (pure aluminum coating) will prevent corrosion while in your shop environment. Pure aluminum forms a protective oxide layer that is very corrosion resistant, as long as moisture etc. is not held in contact with it. As for priming the exterior surfaces, there is a short time recommended between priming and application of topcoat, so priming months (or years) before you finally paint will mean the primer will need to be removed and reapplied or refreshed (weight) prior to applying the paint.

+1. What Mark said.
I would recommend painting or at least priming interior at some point. Much easier to do during construction.
As he said, most paints have a window for maximum chemical bonding so check with the manufacturer.

[Mel]

Do not prime exterior surfaces until ready to paint. Whatever primer is used during painting must be compatible with the top coat. Corrosion will not be a problem. Our earlier kits had no "blue plastic" and they are just fine.
Many production aircraft are left unpainted for life.

[RV7A Flyer]

I had originally planned to do a polished aircraft, so left the blue plastic on (used the soldering iron method to "cut" strips along rivet lines) until final assembly. No corrosion, but I'm in a pretty dry environment. YMMV.

Primed all interior (and exterior faying) surfaces with AKZO (but I did not bother to alumiprep and alodine the interior of the skins except for those that would be exposed (not covered by the Classic Aero Aviator interior), which I painted to match the Van's stock powdercoat color. Ribs and other non-alclad parts were prepped and alodine'd before primer. PITA, but if anyone ever looks in my aft fuse or in the inspection panels, etc., it looks *great* LOL!

Polished aircraft plans? Out the window after the first few flights . Had the plane painted, and I believe the paint shop does a complete acid prep/alodine prior to priming and painting. So no, don't worry about the exterior surfaces.

[David Paule]

I'm building an RV-3B slow-build project. Since few of these kits are sold, parts set on the shelf longer at Van's before being shipped, and since it's a slow-build, they set longer in my shop, too.

Although I live in a comparatively dry climate and corrosion's not typically an issue here, I've noticed some mild corrosion here and there under the blue vinyl. It's typically where the vinyl's not sticking perfectly for any number of reasons. I haven't had a real problem removing older vinyl, although I've frequently needed to cut it into strips and remove it that way. I use a soldering iron for the vinyl cutting. The vinyl adds some welcome scratch protection, and I like it for that.

To me, the main question appears to be the choice between scratches on the surface and corrosion: take your pick.

Dave

[Z-EDD]

Originally Posted by docjefft

1. When do outer surfaces get primed? I know some folks leave the blue plastic on the exterior skins (except where the rivets go) throughout the build. But some of the documents I've seen online say to remove the plastic asap.
2. If you do remove the plastic early on, how is the exposed aluminum protected? Just by the alclad properties? Won't some corrosion occur that will require extra prep before exterior paint is applied?

I think you may have a miss-understanding of the purpose of the blue vinyl. It is for scratch/ abrasion protection, not corrosion. indeed it has been shown to cause/ promote corrosion if moisture becomes trapped beneath it, one of the reasons given for removing it early. The main reason for leaving it in place is if you intend to polish the exterior. If you don't then there is little value but considerable time and labour to remove the strips of vinyl along rivet lines.

[docjefft]

Thanks to everyone for the helpful info. Can't wait to get started!