[Harland E. [n.m. u.s.a.]]

Now that all the dimpling and fluting and straightening on the ribs is done we plan on primering in the same fassion that the Van's Q-B's are done.We know that scuffing with the Scotch-Bright before would be optimum but is it absolutely nesessary with the P60 G2 self etching primer?? We live in the desert and know that alot of guys out here dont bother with any primer at all.I would love to save a little time if I could.My primer war is over and I lost,(or won),so I don want this thread to turn into another battle please.Thanks from Harland and George.

 

[GAHco]

Your location

You may live in New Mexico, but are you going to go anywhere?

a. Near the coast.

b. A rainy Place.

c. Somewhere with air pollution and moisture.

Just a few things to think about.

I am priming even though I have years of maintenance experience and have seen great looking aluminum inside of planes based in areas you would think would be corroding them, and some that had corrosion even with what looked to be adequate priming

All in all it helps, but its not a guarantee.

Beleive it or not I think most of it has to do with the quality of the alclad and how the Alum sheet is handled before and after it is manufactured.

If you are going to prime, do whatever you can to make it stick, otherwise its just a poor coat of colored paint.

I do strongly recommend priming the parts that are not alclad.

Whatever you do, Have fun!

 

[Stephen Lindberg]

I do

Scotch Brite gives the aluminum some "tooth", microscopic ridges and valleys that promote mechanical paint adhesion. You have to clean the aluminum to get the grease off before you paint, and that requires rubbing with something. Might as well be a Scotch Brite pad. BTW, when I do a big batch I hook a garden hose to my hot water tank and run hot water out the door to my picnic table/work bench on the patio. I use neoprene gloves, 409 cleaner, hot water, dry with clean bath towels (generously donated by Mary), and never touch the clean metal without gloves. I shoot self-etching primer the same day. This method has worked well for me. Paint won't stick well unless all the gease and oil is removed. The stamped ribs are pretty oily. 409 works much better than dish washing detergent, in my experience.

 

[TerryWighs]

Scotchbrite works well...and will prepare the surface for Alum-prep, and alodine treatment before priming. Regarding "409"....bit a caution here....I think that stuff has an ammonia base, and can be corrsive????

 

[rv9av8tr]

Scotchbrite & prime

I scotchbrite everything, including alclad surfaces, wipe down with Acteone then primer with SEM self-etching rattle can primer. Works good

 

[Stephen Lindberg]

Sure is

Scotchbrite works well...and will prepare the surface for Alum-prep, and alodine treatment before priming. Regarding "409"....bit a caution here....I think that stuff has an ammonia base, and can be corrsive????

Yes, 409 will corrode aluminum. So will many harsh cleansers. Use copious hot water to rinse them off. I have found acetone to leave a film, MEK less so. Naptha (Coleman lantern fluid) leaves a pretty clean surface. The auto paint store has products (Preps-All, for example) that are made for degreasing prior to painting that seem to work best of all. I like 409 and hot water for large batch cleaning and I save the Prep$$-All for small jobs. Works for me.

 

[SvingenB]

I know that many builders don't want to mess with primers on the underside of thier skins because of the Alclad, but all it takes is a tiny scratch on it and you have an "open wound" waiting for corrosion to set in and work its way around.

This is not entirely correct. The main purpose of alclad is for the outer layer to electrochemically protect the core. The difference in electric potential is around 100 mV between the core material and the surface material. At scratches, edges, holes and so on, the outer layer will protect the core by sacrificing itself. Corrosion in alclad will allways go out lateral on the outer layer instead of attacking the core. Alclad material that looks old and corroded still have full strength and full corrosion resistance.

I prime the inside myself, but I just can't help thinking that what I am doing is like putting a layer of old and dirty cloth on a duck that already has a perfect water repellant, heat insulating coating of feathers. On the outside it is a different story, because the metal also has to be protected from chemical and mechanical abuse.

 

[RadioShack]

Cross Hatching & Priming

I personnaly scuff the parts with a Scotch Brite pad (Scuff one way then perpendicular...kinda like a cross '+'... not a wax on - wax off motion... that's another thing all together.) then clean them with a commercial degreaser. I chose a more environmentally friendly one (not because I'm a tree hugger but because I didn't want to be stuck in a garage during the winter breathing chemicals). Then I use a Self Etching primer in a rattle can. I'm pleased with the way it turns out and am very happy to save the time.

 

[RScott]

Another vote for the method Mike Rhodes uses, except I don't necessarily use self etching primer--the Scotchbrite does the etching for me. Simple, doesn't take a lot of time to Scotchbrite, clean with acetone & spray.

Richard Scott
RV-9A Fuselage