Did you paint your fuselage stringers?

[southwind32]

Since the fuselage stringers are aluminum, I'm curious if you painted yours? I think most people don't paint their spars, or door frames prior to covering. So why paint the stringers? Thanks
Brian

[efwd]

I primed all those surfaces you mentioned. Its all about corrosion. The only raw aluminum my SS7 will have is the electrical trays behind the instrument panel. I don't live too far from the ocean, probably far enough to not be concerned but I will be going to the locals right on the coast as well as Catalina Island.
Eddie

[David47]

Like Eddie, I'll be priming most aluminium parts before covering etc. It doesn't take much more effort to do and besides that, anything you can do to help prevent potential for corrosion is, imo, worth it.

[Bud Davidson]

Re: Corrosion.

My Ford V6 converted to an aircraft engine was spectacular with Ford blue painted block (steel) and polished aluminum heads, manifold and accessories. Great in Pennsylvania.
One month in Florida it was horrible.
I cleaned and painted everything upon return to Penna.
My Kitfox has epoxy primer on ALL aluminum parts because I now live in Florida. I even epoxy primed the radio and transponder trays.
FWIW
Bud
IV 1200
912 ul

[jiott]

I also epoxy primed my aluminum stringers, spars (inside & out), and door frames. I just brushed it on; no spray mess.

[PapuaPilot]

I bought my plane second hand when it was about 14 years old. I don't know when the first owner painted the stringers, but there was filiform corrosion on them, under the hand brushed epoxy paint. I sanded them and repainted the stringers with epoxy primer. The first owner lived near Salt Lake City and the California coastline.

Like others have said it is about preventing corrosion.

[N213RV]

As another data point, I also primed mine with epoxy primer.

[efwd]

Ok, now I know more than I ever cared to know about filiform corrosion. How can you possibly build these without learning so much. Of course you just not become a member on a forum like this. Awesome.

[Esser]

I did not paint my stringers. However, I did epoxy prime in and out of the spars.

[southwind32]

Has anyone used an airbrush to shoot epoxy primer? I was thinking about giving it a try just to do the stringers.

[efwd]

I used an HVLP from Harbor Freight. Very small gun not quite an airbrush but for $8 on sale it was a steal. I did all the wing parts with it as well. I have two of them thinking it was going to plug up but it worked pretty sweet. https://www.harborfreight.com/air-tools/paint/20-fl-oz-hvlp-gravity-feed-air-spray-gun-62300.html
I guess you would have to get a compressor also if you don't have one. I don't know why you couldn't use an airbrush though for that small amount of work.
Eddie

[rv9ralph]

When I was working on my RV9 project, I primed everything in the beginning. I used an airbrush. The advantage with the airbrush was reaching in the inside of flanges. You could get to the inside of bend without heavy buildup on the flanges. You just needed to make more passes to get good coverage.

Back when Cessna started to use Polyurathane paints, the used a conversion coating (alodine) to protect the aluminum before they painted. Their process did not allow the conversion coating to completely dry, causing filiform corrosion to form under the paint several years later.

Several things to consider when priming. First, primer is designed to be used under a finish coat to assist with adhesion to the material. Because of this primers are usually pourous. This will attract and adhere dirt and moisture. Be sure to use a product that does not do this (epoxy type primers usually will meet this requirement).
Another thing to consider with primers, is if the surface of the material is not properly prepared the primer will not stick (I have seen primer flake off). If this surface is what you will be adhering the fabric to, the bond of the fabric will only be as good as the bond of the primer to the underlying material.

Just some thoughts.

Ralph

[David47]

Agree with Ralph. The comment about surface preparation in particular is fundamental and this applies to both paint adhesion and in the case of bonded joints, adhesive application. I've seen paint just rub off after being applied with no or incorrect surface prep and adhesive develop about 1/4 of its shear strength for the same reason. From a previous life, we used to do Alodine followed by epoxy prime. That's the practice I'm following for my build.

[Cherrybark]

Well bother. Happily, I still have a little Poly Fiber Epoxy Primer left over from painting the spars and trailing edge strips. Wish I had though of painting the stringers before pouring out the left over, mixed product.

[efwd]

From what I read, a zinc based product is more preventative against the filiform corrosion anyhow. I can say that if you use a heat gun to dry the zinc chromate so that you can get the aluminum painted more quickly, the paint and zinc chromate will pull right off with simple masking tape.