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Alodine and/or Zinc Chromate Conversion Coating Needed for Homebuilt Aluminum Airplane?

2005

Hello:

I will be building an aluminum airplane, all 6061 T6. I live in Bellingham, WA where the airport lies about a mile off the saltwater. I'm not sure how important this is, since I would think no salt would travel further than the reach of a liquid saltwater mist. I'd think that's on the order of a few hundred yards.

It does rain and drizzle lots here, though. I plan on leaving the plane outside exposed to the elements. I may paint the outside of the plane, but probably only after a year or so.

Some people say don't bother with treating 6061. It won't corrode much in 20 years. Others say acid prep, then Alodine. Some paint after Alodine, some in place of it. Some apply a zn chromate coating on mating surfaces, including dipping rivets with and without alodining.

The easiest for me to do is acid prep then Alodine. There is Alodine 1001, which doesn't change the color. If I do this, how durable is the finish? Would it withstand polishing (I'm not sure what is involved with polishing, either)? Can I safely omit zinc chromating?

Finally, I've heard of an oily spray of sorts that can be used, although seems like this would be messy and could get rubbed off.

Thanks for helping me out,

Dan Morehouse
aluminum finishing - Bellingham, Washington, USA