Fuselage Corrosion

[jdeadly]

Question:
I read the Stitts pamphlet about airframe prep and I decided to do the sandblast/wash primer/epoxy primer process. I applied Aero Tech products as specified and the end result looked fine.....for about 5 years. The airframe has been indoors the entire time (although subject to South LA humidity) and rust is popping through the primer. I'm glad I have not gotten around to covering the thing because I would now have to start all over again. I did the wash primer thing because it was recommended for seaplanes, but the process has totally failed.
Any advice on a finishing procedure that will have a bit more longevity? I am resigned to the fact that I will have to sandblast again, but I will definitely not use the same method of painting again.
Thanks for any advice you can give.
John

[Jim Herpst]

Re: Fuselage Corrosion

Whew Now I am scerred as hell too. I just finished wire brushing and using white epoxy primer on my 1940 fuselage for my clipwing. I did not use any wash primer... wonder if THAT is what screwed you up OR does the epoxy primer need ANOTHER coat like a good top coat of aerothane? I sure as hell hope not (more weight). I live in South Carolina and we get our share of humid temps too ! My last taylorcraft 94984 was a beauty and I believe had a top coat over the whole fuselage AND IT WAS A FAT PIG AT 804 POUNDS !!
Ok it did have all the luxery interior items :carpet door and side upolstery uplostered hat rack ,very nice dope job (smooth and shiny...lots of coats) Vans aircraft old STCd wheel pants (fiberglass).... AND IT WAS A FAT PIG!! SOO experts should we put on a good top coat and stay fat ?? I know my 1940 fuselage was rust free as possible BEFORE I attempted to put on the epoxy. I assume the gentlemans above was also some 5 years ago before he painted his.

[paulnuss]

Re: Fuselage Corrosion

I used Randolph Epibond epoxy primer when rebuilding my '46 BC12D-1, sandblasted and painted in 1981. This primer is an etching primer; no need to use anything else underneath it. These many years later it is still in perfect condition, no rust, no peel, no nothing. It is dope-proof when cured. It cures very hard, and doesn't scratch or scrape easily. The white finish is sort of off-white, and I think would show any problems such as rusting or cracking early. My storage conditions are good, a relatively dry hangar in Pennsylvania, though we aren't insulated so there is the occasional sweating due to temperature changes and humidity. They also make a "zinc chromate" green-appearing primer called Rand-O-Plate, which is also a two-part curing epoxy etching primer.
There are other brands out there, but this is the one I have experience with, and could recommend.

[jgerard]

Re: Fuselage Corrosion

If you are NOT using a primer/sealer, you must spray some kind of sealer/paint over the primer to keep the moisture out. Most primers are NOT meant to be left without a topcoat and are designed to provide a surface for that top coat to stick too. Etching primers work well on materials like aluminum that otherwise most paints won't stick to for long.

Jason
N43643

[Jim Herpst]

Re: Fuselage Corrosion

Paul, Whew thats what I used too. Sound like I ll be ok without a top coat as it sounds like the epoxy is a primer/sealer like John says. I can do a poly top coat I just hate to add any weight as I am trying hard too keep light as makes sence. John do you agree that the Stitts white two part epoxy primer is also a sealer? (seems hard as heck to me like Paul says and appears to have a sheen to it like a sealer would ) Anyone else care to give their opinion on the product mentioned?

[paulnuss]

Re: Fuselage Corrosion

With all due respect to the gentleman who said the Randolph Epibond would need another "sealer" coat, I don't think so. It seals and shines; it is so hard you can barely scratch it with a knife blade; agricultural applicators use it to coat metal parts they don't want to corrode from their chemicals, which can eat most paints alive. And, 24 years later, it is still the same as when I put it on. This isn't automotive primer made to fill and sand and top-coat; it's not zinc chromate; the etching part of it allows it to attach to aluminum of course, but also very well to steel.

[jdeadly]

Re: Fuselage Corrosion

Thanks for the posts, looks like I'll do the etching primer thing and ignore everything about the Stitts process.
I think I'll cover with Ceconite and dope.
Thanks again,
John

[paulnuss]

Re: Fuselage Corrosion

Just to be clear: there are etching primers which need a topcoat, and which are easily soluble by other paints and/or dope. I was speaking specifically of Randolph's Epibond and Randoplate 2-part epoxy primers. They indeed are etching primers. But, they also cure hard and impermeable to penetration and solvents.

[Don Eide]

Re: Fuselage Corrosion

John,

I'd call Aircraft Technical Support, Inc.
Jim and Dondi Miller.

https://www.poly-fiber.com

1-877-877-3334
They are very nice people who can probably tell you what's wrong.
I have used Stits/Poly-Fiber since the early 70's, and have not had any problem. I just checked an airplane I epoxy primed with EP-420 in Dec. 1989, and another I epoxy primed in Feb. 2002. Both look like new.

Don

[Robert Lees]

Re: Fuselage Corrosion

If using Stits two-pack epoxy primer (which "glazes" when cured), it does not need a top coat. Any "unglazing" (or pure matt finish) primer probably does.

(Glazing primers require a little sanding to break the glaze before any further coats)

I would very strongly suggest reading the instructions...most paints do exactly what it says on the tin.


Rob

[Jim Herpst]

Re: Fuselage Corrosion

Ah Robert ever the steady hand on the rudder old boy. Thank you for your expertise and explanation of the "glaze" item. Having screwed around painting cars from I was 12 to 17 it looked to me like the Stits epoxy primer with its "glazed" finish would handle all the *#!@ one could throw on it. I am ready now to proceed. I would suggest to the gentleman that thinks he needs to use the dope process to contact Jim and Dondi Miller as already mentioned in an earlier e-mail. They will probably tell him what I would but I refuse to as its up to the owner in the end to do his thing. Right or ...within a tight judgement wrong. By the way ol fat 94984 was dope and looked great. I would not have another fat doped up plane again having said that....your milage may vary...!!! Best of luck to all . In the end lets just fly em and enjoy em!!

[mhorowit]

Re: Fuselage Corrosion

I just finished wire brushing and using white epoxy primer on my 1940 fuselage for my clipwing.

Jim - I've read about stress risers and you mentioned wire brushing which obviously is going to make scratches. Ref the past thread on 'scratch sensitivity of 4130' , are you not worried about scratches as long as your fingernail won't catch, or did you further smooth the surface? - Mike

[mustang]

Re: Fuselage Corrosion

i also live on the gulf coast and all my experience with two part epoxy primer
says to put a top coat on it. i recovered a colt twice, the first lasted 7 years. covering was still good, but the frame was rusty. i had just finished
sandblasting my taylorcraft frame just over a year ago. did a real clean job of blasting and priming as i went, since primed what i blasted that day. now a year later i have some rust peaking through. this is with the randolph two part, good shiny finish.
i have reached the conclusion that in this very humid climate that a sealing coat is very necessary.

[Jim Herpst]

Re: Fuselage Corrosion

Mike Stress risers. ,,, Sanded smooth finish with emory/wetdry sand paper smooth as hell before painting...lots of work....

[mhorowit]

Re: Fuselage Corrosion

Mike Stress risers. ,,, Sanded smooth finish with emory/wetdry sand paper smooth as hell before painting...lots of work....

Thanks - MIke
But scratches smaller than can be caught by fingernail don't count, right? - Mike