Must Prime Nutplates?

[Brantel]

Is is necessary to prime nutplates? Will they rust if you do not?

My gut is yes and yes but this brings up the fact that most primers are not sealers so what does it gain you to prime them?

They look like they have some kind of black coating on them, is this some kind of protection?

So far I have primed mine but if it is a waste of time, let me know.

[cjensen]

Hmmm, if so, I'm in trouble (as are most builders...). I have primed exactly none of mine. I don't think I've seen any nutplates primed on any production airplane, unless it happened to be in an area that needed some protection after being assembled. The nutplates on my 38 year old Cherokee (since sold...) were bare, and still looked new.

[Captain_John]

The coating on them is BLUEING. You know, like on a gun...

Blueing is a process which oxidizes the top layer and prevents further oxidation (rust) from happening.

Painting them is not a bad idea and I have painted most of mine. I dip them in the leftover product and hang them to dry. You should try dipping yours too!

(cleaned up and made G rated voluntarily!)

CJ

[chaskuss]

Originally Posted by Brantel

Is is necessary to prime nutplates? Will they rust if you do not?

My gut is yes and yes but this brings up the fact that most primers are not sealers so what does it gain you to prime them?

They look like they have some kind of black coating on them, is this some kind of protection?

So far I have primed mine but if it is a waste of time, let me know.

Brian,
The coating on the nutplates will protect them from high humidity, but not actual liquid water. I painted mine. You can simply use spray can paint to coat them. I simply used the left over epoxy primer and PPG Delta top coat (Vans powdercoat gray) that I used for the interior. I made a jig out of a piece of plywood and some nails. Others simply lay them on screen door screening to paint. FYI, if your primer will dry to a gloss finish ( heavy coat or 2 coats), it WILL form a moisture barrier. It is the flat finish of the primer that allows moisture to penetrate it.
Charlie Kuss

[G-force]

FWIW, I primed mine.

[az_gila]

Originally Posted by chaskuss

Brian,
The coating on the nutplates will protect them from high humidity, but not actual liquid water. I painted mine. You can simply use spray can paint to coat them. I simply used the left over epoxy primer and PPG Delta top coat (Vans powdercoat gray) that I used for the interior. I made a jig out of a piece of plywood and some nails. Others simply lay them on screen door screening to paint. FYI, if your primer will dry to a gloss finish ( heavy coat or 2 coats), it WILL form a moisture barrier. It is the flat finish of the primer that allows moisture to penetrate it.
Charlie Kuss

Charlie... if they are true NASM21047 (was MS21047) nutplates, then they are rated for the Mil-Spec salt spray test.... and should take actual liquid water...

I have a feeling that some we buy are to a commercial specification (the K1000 designation) and not as well protected. Aircraft $pruce isn't really clear which version they sell....

gil in Tucson

[chaskuss]

Originally Posted by az_gila

Charlie... if they are true NASM21047 (was MS21047) nutplates, then they are rated for the Mil-Spec salt spray test.... and should take actual liquid water...

I have a feeling that some we buy are to a commercial specification (the K1000 designation) and not as well protected. Aircraft $pruce isn't really clear which version they sell....

gil in Tucson

Hi Gil,
I've seen plenty of 10 -20 year old rusty nut plates in the interior of certified aircraft (Mooney, Piper, Cessna), so I doubt that coating will last forever. Even cadmium plated hardware eventually rusts, as the plating is degraded by the environment. For folks in the middle of the country, the stock finish is probably good enough. Here in Florida, or any southern coastal area, heat, humidity and a salt air environment make quick work of that stuff.
If someone wants nutplates with improved corrosion resistance in stock form, simply add a single number to the last digit of the MS part number. An MS21047-L08 becomes an MS21048-08. This change in number specifies a corrosion resistant part. Either cadmium plating or fabricated from stainless steel.
Charlie Kuss

[gmcjetpilot]

chaskuss: I have to agree. Nut plates are either Cad plated (cadmium) or passivated. Yes a light prime would improve corrosion resistance. It will add little weight by will take extra time. Do it if you like; it will not hurt. However unless you're building a float plane for salt water ops, your RV airframe will out live you.

Besides you are really more worried about the base material, the aluminum. You can always replace a nut plate. Nut cad/passv nut plates against aluminum, especially clad aluminum, double especially if you prime that clad aluminum, are pretty safe corrosion wise. I would lean towards priming the aluminum under nut plates before the nut plate itself. Clad, Cad, passivated coatings all resists corrosion, primer just adds further protection. However the reason for all the coatings of the meaterials is corrosion protection. Do you need to add to it? Not really. Do you want to do it? That's a personal choice.

If you feel like you must prime the nut plates, do it all in one shot. Take EVERY nut plate in your kit out, clean them in lacquer thinner, dry, lay them all out, shoot them with a very light primer coat, wait, flip and prime other side lightly. Don't over do primer because it will mess the threads up and make getting the 3/32 rivets in more difficult. Than you have to spend more time cleaning the threads and rivet holes out. It will take time and effort but you will have the best darn nut plates in all of RV land.

[az_gila]

Originally Posted by gmcjetpilot

If you feel like you must prime the nut plates, do it all in one shot. Take EVERY nut plate in your kit out, clean them in lacquer thinner, dry, lay them all out, shoot them with a very light primer coat, wait, flip and prime other side lightly. Don't over do primer because it will mess the threads up and make getting the 3/32 rivets in more difficult. Than you have to spend more time cleaning the threads and rivet holes out. It will take time and effort but you will have the best darn nut plates in all of RV land.

George.... this might only help a little. If the nutplates are passivated (which I couldn't find in the NASM21047 specification), some of them also have "dry film lubricant" applied.

Using an acetone wash would probably take this film off, which is part of the corrosion protection, and I presume makes the screws easier to insert.... Be careful you don't go one step backwards before going forward....

Does anyone know the actual part number of the nutplates we get? Are the K1000 different from the Mil-Spec? ....and if not, which dash number is it equivalent too?

If we are worried about cad. plated parts rusting, then every bolt in the plane is now suspect..... which might be correct in FL...

gil in Tucson - something to ask the vendors at Copperstate this weekend..

[chaskuss]

Originally Posted by gmcjetpilot

chaskuss: I have to agree. Nut plates are either Cad plated (cadmium) or passivated. Yes a light prime would improve corrosion resistance. It will add little weight by will take extra time. Do it if you like; it will not hurt. However unless you're building a float plane for salt water ops, your RV airframe will out live you.

snipped

If you feel like you must prime the nut plates, do it all in one shot. Take EVERY nut plate in your kit out, clean them in lacquer thinner, dry, lay them all out, shoot them with a very light primer coat, wait, flip and prime other side lightly. Don't over do primer because it will mess the threads up and make getting the 3/32 rivets in more difficult. Than you have to spend more time cleaning the threads and rivet holes out. It will take time and effort but you will have the best darn nut plates in all of RV land.

George,
I generally did about 100 nutplates at a time, depending on how much excess primer I had mixed. That way, I made use of the excess primer. I agree that priming all the nutplates at one time would reduce the work involved. I used aerosol brake parts cleaner, rather than lacquer thinner. The brake parts cleaner is easier to use and leaves no residual film. I'm sure that most solvents will work.
Regarding Gil's mention of dry lube on the nutplates, that is what the L in the first position of the part number suffix denotes. ie MS21049-L08
I don't like the idea of running a tap through the nutplates prior to first installation of the screw. I've found that coating the screw threads with Boe Lube or Never Seize and dipping the tip of the #2 Phillips screw driver in valve lapping compound works great. The lapping compound gives the screw driver extra "bite" in the screw head.
Charlie
Charlie