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Are you guys primering the steel rivet holes before riveting?

B

Brad_in_Indy

Member
Just looking around at a lot of builders' logs and I notice that the steel parts (elevator, center HS) don't appear to have been touched with primer before riveting/bolting them onto the aluminum structure. Unless I'm doing something wrong, the powder coating came right off inside the holes as they were final drilled to the aluminum, so some kind of primer barrier needs to go there before riveting, doesn't it?

Cheers,

Brad
 
I like you already Brad, you pay attention to details! Yes put a dab of primer in the holes to prevent rust!
 
I had similar concerns throughout the build, and was never quite sure what to do with these holes. In many cases, such as gear weldments, the holes need to be reamed just a few thousandths to allow the bolts to slide in (and yes, I checked those with the close tolerance bolts so I won't run into a major hitch down the line). So after reaming holes on various parts to a good, tight fit, the inside of the hole is now bare steel. But if you put primer or paint on it, it'll be too tight a fit to get the bolt in! Open it up enough to put primer on it, and now you don't have a tight fit...

I opted for tighter fit, no paint on the inside of the hole...
 
Rivet holes in steel

Primer in the hole is a good start, but as pointed out, could be too tight. Steel in steel forming rust is less dangerous than aluminum rivits in steel or steel bolts in aluminum because of aggressive corrosion ( dissimilar metals ?). Boesheild grease, vaseline, Grizzly table saw antirust are good option for a tight hole you want to protect.
 
Or install "wet", dab some paint in the hole and on the rivet/bolt shank then install.
 
I "wet set" the rivets in the powder coated steel parts by squirting them with Tempo zinc chromate just before I set them. I also give the hole a little squirt before inserting the rivet. After the rivets are set, you can wipe off the excess.
 
If you did not prime or grease every hole(like some of mine), then use LPS-1 or -2 after final painting of plane(hopefully in the next few months for us). It won't fall apart in a few months unless you live near the ocean. I used the thicker LPS-3 on wing and gear leg bolts. Remember to keep most threads dry except spark plug threads when torquing to specs.
 
On steel parts, Rustoleum cold galvanizing spray works well. Lots of zinc solids, which is apparent when you heft the can! Rustoleum warns against painting over it though, so while it's suitable for protecting holes like the topic of this thread, it shouldn't be used as a primer. I sprayed it into the bare holes, and occasionally on shanks of bolts/rivets going through the holes, then installed wet.
 
I would bet that the majority of the fleet did nothing here. It is easy to do and it sounds like a good idea so I would not discourage it.
However, just a data point; on my G.46, 60 years old, more corrosion issues than you could imagine, there is absolutely no corrosion on the inside of any holes, aluminum or steel. They are pristine. Even the material below the head is perfect. The holes where not primed or treated in any way. This is an airplane that was out in the weather for many, many years, as a gate guard and then left unprotected for many more years before I started the project. I could not imagine a worst case example.
FWIW
 
I used Mastinox

Its like wet pasty Zinc Chromate primer that never hardens.

I got it from a helicopter mechanic nicknamed "Bubba dog lips"

Really, no kidding:eek:
 
RTV

I've thought about this also, but never did anything about.

How about a little dab of RTV and install the rivets wet as was suggested with the pro-seal? It would be easy to do.
 
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