[jlfernan]

I was in a rush today and may have primed(Marhyde rattle can) the inside skin around the air vent NACA duct abd down to the floor without wiping it down first. The primer dried a little rough but smoothed easily with a scotch-brite pad. I think the skin may have been dusty. What's the worse that can happen other than the primer not adhering? It seemed to be on pretty good when I scotch-brited it.

 

[prkaye]

good question

I'd like to know the answer to this too...can applying self-etch primer over an unclean surface lead to more serious problems than just poor adhesion?

Also, what is the recommended method of cleaning parts before applying self-etch primer?

 

[jlfernan]

I'm also curious about the factory primer on the QB's. I know the interior has a wash primer from the factory, but do they prime beneath stiffners and such before assembly?

 

[RV10Pilot]

I'm also curious about the factory primer on the QB's. I know the interior has a wash primer from the factory, but do they prime beneath stiffners and such before assembly?

On my QB RV-10 fuselage they did not prime behind many of the removable side panels. It looks like the fuselage was assembled and then primed. So I would assume that they did not prime under the stiffeners.

In the photo below you can see were they primed and where they did not.

Larry
http://lrosen.nerv10.com

 

[jlfernan]

Any painters out there care to chime in?

 

[Aden Rich]

Priming

If you really want to get a good adhesion with primer here is the routine.
1. After all work has bee completed (drilling, deburring and dimpling) rough the parts up with red scotch bright pads. Just take the luster off the alum. All you want here is a little mechanical adhesion.
2. Clean all parts. Blow off first with air.Then use acetone or another cleaner. Do not use a wax remover or degreaser. Alum is porous and will soak this stuff up which could lead to pinholes or fisheyes. Also, us CLEAN towels. I use the blue shop towels that can be bought at Home Depot. Then I just toss them in the trash.
3. Static wipe down the parts. These can be purchased at the auto paint store. Wait for the static wipe to evaporate.
4. Primary tack cloth-don't push too hard, just a gentle brush over the surface.
5. Secondary tack cloth the parts-both of these can be purchased at the paint store also.
6. Paint the part. If you get a spot you don't like. Wait till the paint dries, then scotch bright is again and repeat the process except for the acetone part. That will just make another mess.
Hope this helps.

 

[WSBuilder]

Good Adhesion AND Corrosion Protection

If you really want to get a good adhesion with primer here is the routine.
1. After all work has bee completed (drilling, deburring and dimpling) rough the parts up with red scotch bright pads. Just take the luster off the alum. All you want here is a little mechanical adhesion.
2. Clean all parts. Blow off first with air.Then use acetone or another cleaner. Do not use a wax remover or degreaser. Alum is porous and will soak this stuff up which could lead to pinholes or fisheyes. Also, us CLEAN towels. I use the blue shop towels that can be bought at Home Depot. Then I just toss them in the trash.
3. Static wipe down the parts. These can be purchased at the auto paint store. Wait for the static wipe to evaporate.
4. Primary tack cloth-don't push too hard, just a gentle brush over the surface.
5. Secondary tack cloth the parts-both of these can be purchased at the paint store also.
6. Paint the part. If you get a spot you don't like. Wait till the paint dries, then scotch bright is again and repeat the process except for the acetone part. That will just make another mess.
Hope this helps.

Everything you said is correct for adhesion quality, but a conversion coating (Alodine) is also needed for the best corrosion inhibition.

 

[KTM520guy]

For paint prep I wouldn't use the blue towels. They have a tendency to leave lint especially around rivits. I do go through a lot of them though. Mostly for general cleaning. For paint prep I use a different blue towel that is made by Dupont. It's 100% lint free. Expensive but worth it for complete paint jobs.

Self etching primer would be great to use on the interior. If thats what you end up using do not use any alodine. Only use alodine if you are using a standard primer.