Painting Over Alodine Coatings

Bartman

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Would anyone happen to know for sure what it takes to make paint stick to aluminum that has been alodine coated? Is it enough to scuff and clean them? Is a primer coat necessary before paint or will paint stick to the alodine?

The four prong inspection plates from ACA aren't sent in primer anymore, they're alodine coated. Still $11 each though so it's a bargain!

Thanks!
 

Bob Turner

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Use the dome type - less than $2 each - and a #4 PK screw and Tinnerman nut on the front of each. Easier, better looking. I have both types on my Decathlon.

Piper domes - now $22 each - were better, because they had "stop" rivets on the spring. But they were not $20 better.
 

Bartman

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32 inspection plates in four different styles, the benefit of converting from wood spar wings!
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Bartman

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Use the dome type - less than $2 each - and a #4 PK screw and Tinnerman nut on the front of each. Easier, better looking. I have both types on my Decathlon.

Piper domes - now $22 each - were better, because they had "stop" rivets on the spring. But they were not $20 better.
A tinnerman with a hole through the plastic ring?
 

Bob Turner

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Yes. If the plastic ring deteriorates, glue an annulus of .020 aluminum inside, drill #41, and, holding it in place, run the screw through. A day later you should be able to put the plate on and screw the #4 in without loosening the aluminum.

Obviously, punch the hole in the plate about 45 degrees from the spring, and roughly in the middle of where the plastic ring will be.

Some of us use metal instead of plastic, from the get-go. Same for drain grommets.
 

Bob Turner

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Piper used plastic on all openings, and the PK screws were simply held in the plastic. But after time, plastic inspection rings will crack. Mine are from a 1992 cover job, and every year I have to do the aluminum annulus on one or more. Still, it is the only way to keep the plates on the airplane. I even have the four spring plates so attached.