Primer

[dbdevkc]

Anyone here used self-etching primer? I am considering using it on any mating surfaces. Other than the Monett's stating it is unnecessary, it taking extra time, and adding a bit of weight, are there any technical reasons to not do it?

Kevin
Waiex 169

[Andy Walker]

I don't think there is any technical reason not to prime parts. I have heard some say that priming with no topcoat can actually promote corrosion, but I'm not sure if that applies to all types of primer, or for that matter if it's really true at all.

That said, I'm not doing an corrosion protection on my build. If I were living near the ocean I would reconsider that. But it's not recommended by the factory, and it adds weight, so I'm going to skip it. One thing to consider: how long do you plan to fly the Sonex? 20 years? 30? Less? There are thousands of 50-60 year old Cessnas and Pipers that had no corrosion protection from the factory that are doing just fine, and most of them are Alclad which is not as corrosion resistant as 6061-T6. Just something to think about.

[MichaelFarley56]

I don't think you're going to hurt anything.

I used the gray NAPA self etching primer (number 72##...I can't remember the actual number) on my tail and main wing spars, and then used it on all flanges and mating surfaces in the wings and fuselage. I live in Ohio so it's probably overkill, but fir just a few dollars I didnt think it would hurt anything.

[Sonex1517]

Kevin,

I can't see how it would hurt...

We aren't doing it - but we live in the midwest.

[dbdevkc]

I have been reading on some hot rodder discussion boards things to the effect that using self etch primer by itself will not offer any corrosion protection.

*****
If you ask the manufacturer like I did you can get the correct answer.

Self etch primer is for metal that has not been etched by some other means. So if you are building a something and weld up some brand new sheets of the steel and do not want to sand them you use the self etch primer. The job of self etch primer is to make a good surface for putting the next layer of paint on to the metal. If the metal is already a good surface for a direct to metal paint then you do not need (and do not want) an etching primer.

The etch primer has been improperly thought of as a way to prevent corrosion. I had the local dupont paint store guy try to sell it to me for that purpose.

For most of what we are doing the better solution is to etch the metal. Either with various chemical methods such as Pickle X or metal pre-treats the paint companies sell. We can also sand the metal or even better sandblast. Then put down a nice layer of epoxy to seal the metal from moisture.

*****

You are correct in the use of etch primer. Only for new metal that has not been sanded.

And.....

Yes the paint supplier will tell you anything to sell more paint or material.

*****

I agree, etching primer is extremely OVER rated. So what does etching primer do? It forms a TEXTURE on the bare metal so that paint will mechanically bond to it.

If you have sanded or media blasted the metal, there is NO need for etching primer. The metal has a texture due to the sanding or blasting.

Just cover the bare metal with Epoxy Primer/Sealer and go for it. You can apply your top coats or do your body work right on top of the epoxy.

*****

you wont get any protection from etch primer. moisture will go right through it. use epoxy.

[rizzz]

The etch primers do not provide "significant" corrosion protection by themselves but remember, if they are good enough for Vans to use on the 2024-T4 alum in their quick build kits (Vans uses the P60G2 primer), they must certainly be good enough on the Sonex 6061-T6 alum.

[Andy Walker]

The etch primers do not provide "significant" corrosion protection by themselves but remember, if they are good enough for Vans to use on the 2024-T4 alum in their quick build kits (Vans uses the P60G2 primer), they must certainly be good enough on the Sonex 6061-T6 alum.

No doubt the primer is good enough, since no primer is good enough too! I just question adding the weight, expense, and time of primer when the benefit is questionable. for 2024 it might make more sense, but for 6061 I just think you're wasting time unless you are in a marine environment. My opinion of course. Again I point out that most of the airplanes made by the big manufacturers do not have any anti-corrosion coatings, and many of them have been flying 50-60 years (and are made of alclad). Are you really building your Sonex to last longer than that??

[rizzz]

The etch primers do not provide "significant" corrosion protection by themselves but remember, if they are good enough for Vans to use on the 2024-T4 alum in their quick build kits (Vans uses the P60G2 primer), they must certainly be good enough on the Sonex 6061-T6 alum.

No doubt the primer is good enough, since no primer is good enough too! I just question adding the weight, expense, and time of primer when the benefit is questionable. for 2024 it might make more sense, but for 6061 I just think you're wasting time unless you are in a marine environment. My opinion of course. Again I point out that most of the airplanes made by the big manufacturers do not have any anti-corrosion coatings, and many of them have been flying 50-60 years (and are made of alclad). Are you really building your Sonex to last longer than that??

You're absolutely right.
However, there is one other reason I can come up with to prime your aircraft, resale value.
Even though priming is completely optional on 6061, if you ever plan to sell your Sonex it might be hard to convince potential buyers of this fact, they might go with the other Sonex on barnstormers that was primed.
Then again, potential buyers might favor a lighter Sonex to a primed Sonex, who knows.

[dbdevkc]

How toxic is S.E.P., and what type of precautions need to be taken when using a rattle-can S.E.P. (ie: respirator, etc.)?

Kevin

[Andy Walker]

The etch primers do not provide "significant" corrosion protection by themselves but remember, if they are good enough for Vans to use on the 2024-T4 alum in their quick build kits (Vans uses the P60G2 primer), they must certainly be good enough on the Sonex 6061-T6 alum.

No doubt the primer is good enough, since no primer is good enough too! I just question adding the weight, expense, and time of primer when the benefit is questionable. for 2024 it might make more sense, but for 6061 I just think you're wasting time unless you are in a marine environment. My opinion of course. Again I point out that most of the airplanes made by the big manufacturers do not have any anti-corrosion coatings, and many of them have been flying 50-60 years (and are made of alclad). Are you really building your Sonex to last longer than that??

You're absolutely right.
However, there is one other reason I can come up with to prime your aircraft, resale value.
Even though priming is completely optional on 6061, if you ever plan to sell your Sonex it might be hard to convince potential buyers of this fact, they might go with the other Sonex on barnstormers that was primed.
Then again, potential buyers might favor a lighter Sonex to a primed Sonex, who knows.

Good point! Many of us (myself included) plan to never sell, but times and circumstances change.