More considerations
I decided not to prim Alclad (2024T3?) parts. But I am not sure if ribs are Alclad?
Vans tech support is not open till Monday and I am hoping to get an answer here soon so I can continue to work this weekend. Thanks in advance.
Frank's comments regarding his Zenith do not apply to your RV6 project. RV sheet aluminum is made from 2024 alloy, not the 6061-T6 used in the Zenith series aircraft.
The ribs on my 8A project appear to have an Alclad covering on them. I say this because my wing main ribs were badly scratched. This was due to Vans packing them one inside the other, with no paper or other protection between them. My ribs did not come with a plastic coating [PVC] on them. To polish out some of the deeper scratches, required polishing through the Alclad layer. The layer was clearly visible to me. It reminded me of sanding through finish paint to the primer underneath when repainting a car.
I agree with Richard Bibb's comments regarding dissimilar alloy corrosion. His comments regarding the hydro forming process concern me. I would STRONGLY suggest you speak to someone at Vans to verify that YOUR ribs do or do not come with Alcadding on them.
Are you forgoing the priming due to weight concerns? Or are you trying to keep the labor to a minimum? If excess weight is your concern, I would suggest Alodining your 2024 parts. Even the Alclad items have areas where corrosion can start. Remember that all the edges and the rivet holes have no Alclad on them. They are pure 2024, which corrodes easily. Chromic acid conversion coating [the generic name for applying Alodine, Duradokote, Iridite, etc] adds no weight and GREATLY inhibits corrosion. Naturally, this process will add to the labor required.
Is added labor is the issue? You might consider Alodining JUST your wing parts. I say this because repairing corrosion inside a wing will require HUNDREDS of hours of labor to repair. This is because of the extremely restricted access to the interior of the wings, once they are closed up. You could simply build a new empennage part, if one became corroded in the future. The fuselage allows access to the interior. This will allow a relatively easy repair of most future corrosion on this sub kit.
Some builders prime only the faying [contact] surfaces, to reduce weight. Most corrosion occurs where two pieces meet, such as a skin and a rib flange. Just some things to consider.
Charlie Kuss
PS Richard's comments make me glad I Alodined and Mil Spec epoxy primed all my parts. I live near the Atlantic Ocean in SE Florida [corrosion capital of the world!].