Primer Wars

To say there are some strongly held positions on the necessity and method of protecting the aluminum components of an airplane would be like saying some modern day religious fundamentalists hold differing points of view. No doubt in both cases some people will consider me a heretic while I think I'm pretty much middle of the road. Whether I actually hold centrist positions in either case is something for someone else to judge. Frankly, I've read, thought, considered, asked questions, and formed my own informed opinion - on both topics; airplane primer and religion.

There's a school of though that does a milspec process on every part. This generally amounts to preparing the surface by roughing it with Scotchbrite pads, cleaning the aluminum of all grease and oil, applying alumaprep followed by an alodine treatment followed by a two part epoxy. This not only seems like a lot of work, it is a lot work and takes time. I'd do it though if I thought it necessary.

I'm flying "spam cans" now and when I look behind the bulkheads I generally see bright and shiny alclad aluminum. Most of these Pipers and Cessnas are 30 or more years old. I'm 52. If it takes me 2 years to build this RV-9 and 30 years later, when I'm 84, if the surfaces look as good as the "spam cans" look, my RV-9 will have many years of airworthiness left in the airframe. I'm not sure I'll be doing as well at 84.

This line of thinking leads some bright minds to conclude primer isn't necessary. I'm not in this group, though I think they have reached a valid conclusion.

There's another group of that is looking for something more than no protection beyond the Alclad and the archival protection provided by the first group describe. I'm in this group. Some of the people choose a "wash" type primer, which strikes me as being perhaps the worst of all worlds. It requires a fair amount of work, damages the Alclad and appears to me to provide a good base to paint on but offers little (if any) additional protection. I'm inclined to follow this group in spirit and bow to the time-tested use of zinc chromate as the primer of choice. In the interest of saving weight and money I'm planning to apply it were corrosion is likely - where parts mate and leave the large expanses of Alclad protected sheets of aluminum alone.

Your mileage may vary. You don't have to buy or fly in my machine if this strikes you as a cavalier attitude toward corrosion. Should the plane disintegrate around me at altitude as a result of corrosion, I'll quickly and readily admit the errors of my logic on the way down. In all honestly though, the admission of error will be brief. Most of my thoughts will be focused on those religious beliefs and heading back up.

Don