The new tubes has alclad coating on the surface that needs to be eliminated before painting. You can use etching chemicals, wash-primer, alodine coating or just rub it down with fine sandpaper and scotch brite before priming with Epoxy or polyurethane Primer. It all depends on how the climate is were your plane is operated. In Sweden we don´t have to hi humidity and salt water in the air. Tierras and Akkas was just Painted with Epoxy paint and it last many years. But it needs to be looked after. I think polyurethane Primer is bether than Epoxy Primer because I think it´s more flexible and can withstand erosion better. JAS39 Gripen is primed with polyurethane primer and at many places it is the only paint used. But SAAB uses wash primer/ Alodine on all their parts before priming. But I am not rebuilding a jet fighter… Or do I…?
Jag är ett sätt att tänka.