Powdercoat Removal

Well it seems that 2 steps forward, 1 step back is the theme of my 2nd hand model 5 kit build.

I was doing some powdercoat touchup work on some fuselage tabs and such the other night. Lots of the tabs have sharp edges, and that was where a little line of rust showed thru the powdercoat. (the sharp edge makes the powdercoat in those areas thing to non-existent).

I removed the powdercoat on a few of these areas till I could no longer see surface rust. Well, a few of these, the surface rust kept going along a tube to the firewall mounts.

This powdercoat was so adhered from the surface rust, I would peel it off in one long sliver with a knife.

Not everywhere is like this. I did a sample gouge with my knife elsewhere and the powder-coat is stuck good.

However, this is enough to ruin my confidence in the powdercoat on my fuselage, and I am going to strip and paint.

The good news is the rust I have found comes off with some scrubs of a scotchnrite pad. No pitting.

Can anyone share their experience doing this? Did you use chemicals, or blast it all off? If you blasted, did you blast twice - once for the initial, and a secondary pre-epoxy primer?

It seems blasting only once is ideal since it is metal removal, but tricky since you want minimal time between blasting and primer, especially to keep everything super clean.

Any input appreciated.

When I purchased my Series 5 in kit form from Skystar in 1999, I found my freshly powdercoated fuselage to have similiar problems to what you are finding on yours. Apparently the vendor they used did not adequately prep all the tubing and I found area like you are finding that had to sanded to bare metal and primed/painted. The old kitfox owners (Skystar) had very poor quality control in my opinion as other issues reared their ugly heads during the build. (gaping holes in new fuel tanks that the factory said were pressure tested, poor quality with the quick build wing etc ) From what i hear from new builders now , this is not a problem under the Mcbeans ownership but older unfinished projects that are floating around should always be thoroughly inspected like you are doing. I think you are doing the right thing in taking it down to bare metal and starting over. I would talk to a local sandblasting shop about the project and go from there. I had a small harbor freight blaster that I used to cleanup the suspect areas and that worked fine, but for a hole fuselage i would take it to a blasting shop. Bruce N199CL

Been there!
You need to remove that stuff.
I used some stuff called DZOLVE 15-33r it works great! I stripped the complete plane and gear
used about 2 1/2 gallons at the most. I made the mistake of trying to wash it off to soon. Let it
set. It will work for two or three days. This stuff doesn’t stink and doesn’t burn your skin.
will probably take two applications to get it all. Very happy with this stuff on powder coat!

Eric,

My initial thought is to blast everything to clean metal (admittedly that comes from a person <me> who ordered a bare frame and went with blast-epoxy-aerothane treatmet). Also gives a person a good chance to inspect the welds - I did have to reweld a couple brackets on the skystar vintage airframe where someone got a little overzealous with the TIG welder.

Getting the paint on fairly soon is important to prevent restart of rust.

When I did ours - I did the dirty in the driveway method of blasting (cost saving) then got the epoxy on by the next day and the aerothane on 12-14 hours after the epoxy on the advice of my polyfiber rep - the epoxy and aerothane really bond well that way after the epoxy solvents are gone but before it hardens off. Spraying tubing is interesting - a person has to hit each tube from about nine sides to ensure the best coverage.

I had issues with my 6 when I found it. I had it all blasted clean. Inspected and then re coated. I didn't do it. The guy that did said it took about a pallet of media.

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Thanks all for the feedback.

Encouraging to hear some chemicals will work for removal that sound safe for the average Joe to handle. Will have to run some tests. I wonder if scuffing up the top of the powdercoat (not the the metal) with 80 grit would help accelerate the process?

It's been like this for 20 years, so hopefully a few more months shouldn't hurt. I have a few items I would like to weld on before re-paint during this time anyways, and I'll primer (or maybe just regular spray paint is fine) any bare spots I exposed in the meantime.


I'm doing the longer 7 turtledeck (gives the 5 a larger cargo opening), so I need new rear tabs welded on for that.

I'm also going to add an antenna plate in the area indicated in red to give me ideal spacing between transponder behind the pilot, comm behind the turtledeck, and ADSB a few feet infront of the vertical stab.
Attachment 23813
(note the existing plate in this image behind my red plate is the model 6's comm location, which I would do as it is shorter, but does not give very good antenna spacing.)

I did a complete superstol frame and gear. Just brush it on and leave it sit for a few days. It will look like
it stopped working in a day or less. But let it sit longer. It will turn the powder coat to a liquid that looks like
fresh paint. Hot water pressure washer is the best way to remove the residue. Totally different than any stripper I tried.

Quote:

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Originally Posted by rcbif

I wonder if scuffing up the top of the powdercoat (not the the metal) with 80 grit would help accelerate the process?

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Yes, I believe I found that this would help.

If you want to have the entire frame back to bare metal then take the frame to your local powder coater and have them put the frame into their burn off oven.

They will set it to like 700 degrees for 8 hrs and the paint will literally burn off. They then sand blast it and it's clean.

It probably wouldn't be practical to do a whole airframe with this, but there was some discussion in the forum a year or so ago about removing powdercoat from smaller areas where you wanted to repaint, weld a tab, connect a ground wire etc. I believe it was Scott Noble or maybe someone else who came up with a Permatex or Locktite product (I think it was a gasket remover) that worked real well. A forum search should find it.

I believe it was Josh Esser.

Total newbie here regarding Kitfoxes but I did considerable powdercoat work when I was working on my A&P at the community college. We had some very nice equipment as far as ovens and cleaning equipment. I did the landing gear legs and engine mount for my Mooney and found that, like your mount tabs, there were places where the coverage became very thin at the inside of tight angles on the nose gear truss and the pads for the landing gear pucks. Doing some research I was told that this is a problem because of the electric charge that draws the powder onto the part. The field gets distorted at those edges and junctions so the powder doesn't coat so well. One source said you could brush the powder onto those areas to get better coverage but I have not had a chance to try that. I hear that Van's is having some instances of rust under the powdercoat on their kits. I think I'm pretty solidly in the strip it and paint it with a good etch primer for the base before color.

That makes sence. Even with traditional painting though, it seems paint sicks away from sharp edges.

I visited my instructor who is an a&p while he was stripping a 182 last week. I brought a sample piece (the model 5 antenna mount I wont be using) and he painted on some aircraft remover. About half hour later when I got home, a flathead screwdriver could peel off 90% of the powdercoat to the metal. If it was still wet, maybe even more. When the stripper dries, it seems the powdercoat hardens again.

He also gave me the number to a blasting company that has done a cub before, so I will call them and get opinions on whether they can blast it all in one go, or if it will be beneficial to chemical strip, then bring g it in for blasting.

My neighbor at the airport who just finished the paint phase of his beautiful cub has graciously agreed to let me use his booth and fuselage rotisserie. Gotta love aviation friends...

A few tips on using paint stripper... After applying the paint stripper, cover the area with cling wrap (Saran Wrap, plastic food wrap, etc.) This will keep the area wetted to let the stripper work longer.

DO NOT use a metal blade (screw driver, metal putty knife) to scrape the softened paint/powder coat. Use wood or plastic putty knife to scrape the softened paint.

Rinse the surfaces real well, blow dry with compressed air using proper safety protection.

Ralph

What about wire brushes? Should I go brass for those? If I do chem strip, I assume I'll need somthing like that for the weld clusters.

If you are working on the 4130 chrome/moly, you can use a steel brush, even mechanically assisted (a steel brush wheel on pneumatic or drill motor). Brass should be used if working on aluminum.

The main concern is that you don't use anything so aggressive that it removes metal.

Ralph

One more option for mechanical removal. 3M Roloc bristle disk.

here are some images...

Attachment 23832Attachment 23833

Ralph

Quote:

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Originally Posted by Xengineguy

Been there!
You need to remove that stuff.
I used some stuff called DZOLVE 15-33r it works great! I stripped the complete plane and gear
used about 2 1/2 gallons at the most. I made the mistake of trying to wash it off to soon. Let it
set. It will work for two or three days. This stuff doesn’t stink and doesn’t burn your skin.
will probably take two applications to get it all. Very happy with this stuff on powder coat!

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I've got a sample of this coming to try out. They only charge for shipping and have been very prompt with communications.

I actually got another remover sample from them today, but then I saw that it had formic acid which can affect high strength steels and he confirmed that the 15-33r would be safer for this application.