corrosion through powder coat

[ken nougaret]

I spent 5 yrs building my S7 and have been flying it regular for the last 2 yrs. I ordered my kit powder coated. I am seeing increasing corrosion on the horizontal struts, jury struts, and flaperon counter balance weights. I will do my annual soon and do my best to inspect the hard to see areas. My concern is in the areas i cant see, like under fabric ( maybe the fabric protects?), and the wing struts.
Have others had issues?
Ken

[Bud Davidson]

Ken, Very interesting. I am restoring a damaged kitfox from a kit originating in the mid 90's and found rust hidden by red powder coating. Not on fuselage tubing but as you note, on wing fittings. No corrosion inside wings.

[airlina]

Ken,Way back when I built my Series 5, (it was a 1999 kit) and Skystar was the kitfox manufacturer then, I found similar issues. The first section of my manual was builders tips & pg 1 , paragraph 1 says inspect all powdered coated parts for bare spots and touch up, however more than bare spots, I found evidence of poorly prepped bare metal pre powder coating that had light surface corrosion that caused bubbling of the powder coat. I recall taking all the powder coat off of some parts sand blasting and epoxy priming and repainting. Was not real happy with the lack of quality control back then as it showed up in other areas as my project progressed. Another big one was fuel tanks with manufacturing holes in the fiberglass that their customer service guy said couldn't happen because all tanks were pressure tested. You can imagine how the conversation went from there! Bruce N199CL

[ken nougaret]

Thanks Bruce. These areas that have a problem now showed no issues while building. They looked to be covered fine. This started showing up about a year ago

[ken nougaret]

Good to hear from you Bud!

[bbs428]

I thought only the older kits had these issues?

My 1998 outback kit certainly has them.
It was stored in a heated garage for 20 years. Had it's fair share of scratches and chips.
The powder coat on the bottom of the airframe was shedding like a bison in springtime.
I wire brush/chip away at the coating till I get into clean metal. Then it's "dip and dab" time.
acid brush some Corroseal on it and 2 part epoxy primer when dry.
http://corroseal.com/

On the smaller parts that are corroded, I sand blast them and paint as above.
I hope I get all of it before I cover.

I use Boeshield T9 spray for bare metal, connectors, battery terminals etc.
Leaves a nice waxy residue. I like it a lot. https://boeshield.com/

Other products work just as well but these are the ones I have used.
It's extra work, but that's what this bird is all about, right? Lol.