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Permalink Reply by Chris Aysen on October 19, 2009 at 7:25am

Dave - Chris from south Louisiana; definitely prime the metal (where two pieces meet). Prime the internals of the whole plane. You cannot judge the weight of the finish product by the weight of the primer in the can. Most of the weight will be evaporated out. Good luck and happy building.

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Permalink Reply by Gary Bean on October 19, 2009 at 11:06am

The instructions for my 601 said to prime the surfaces where two pieces overlap, but I opted to cover everything. I used Zinc Oxide primer (purchased at a marine supply store) and mixed it 50/50 with solvent to make it easier to apply. I brushed it on, since it is on the interior surfaces, and have had no problems. Just be sure the surface to be primed is clean, and scuffed up with a scotch-brite pad before applying. I don't know exactly how much weight it added, but I doubt if it is more than 10 pounds. The two-part primers would probably be heavier.

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Permalink Reply by Chumphol Sirinavin on October 19, 2009 at 11:08am

Dave,

Priming one side of the two joining pieces before riveting is a good idea. Anyway, my '96 built CH701 I bought in Puerto Rico had been in a coastal environment and often spent the night outside a roof for some years. During this re-build, when open up the skin, I was much surprised to see that Corrosion X had given the plane a very good protection. The builder rarely used any zincchromate or any other rust protectant. Corrosion is found only in a few places under the rear fuselage. A few drain holes should prevent future problem Now in a land environment, I rivet the pieces and spray Corrosion X later. In certain places where heavy corrosion can be expected ( such as where the steel gear/strut fitting attached to the fuselage side), I spray a coat of zincoxide before closing.

Champ

P.S. Corrosion X is an excellent penetrant, lubricant, and Corrosion filter which confirms to Mil-C-81309E and is perfect for extended Corrosion protection of airframes.

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Permalink Reply by Jim Belcher on October 19, 2009 at 5:32pm

Based on 25 years of aircraft ownership, I'm priming the mating surfaces only. When everything is built and painted, I will treat the inside with Corrosion X, or a similar product that does the same thing.

I've found Corrosion X creeps over all the interior surfaces, and does a darn good job of preventing corrosion. It will make it difficult to get paint to adhere, hence the wait on applying until painted. If I lived near water, especially salt water, I might do things differently.

No, primer doesn't weight a lot, but when we only have 1320 lbs to begin with, every ounce counts, and it also costs money. At least, that's my philosophy.

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Permalink Reply by Einar Arne Kleiven on October 29, 2009 at 9:59am

I am priming with zinc cromate all parts. But when building (some parts) are drilled after the priming of the sheet... So the holes are not primed!! This "problem" am i planning to solve with corrosion X. But one question to experienced X sprayers: how do you get prayed all area inside a wing, rudder, etc...? (drilling holes?)

I am planning to fit floats on my 701, and my flying here in Norway will be on seawater..., how do a 701 (aluminum) aircraft stand up to this harsh envirement? Is it possible to operate a aircraft on seawater, and still have a non-corroded aircraft? ( rinsing with freshwater and care after each use oufcourse )

Einar-Arne Kleiven

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Permalink Reply by Chumphol Sirinavin on October 29, 2009 at 11:22am

Drilling new hole(s) on end rib for spraying. Over-spraying through one end rib, and let the excessive oil flow to the other end. I removed the horizontal stabilizer and elevator from fuselage and kept them standing on opposite ends for some time after spraying before re-installing them in place.
For each of other enclosed sections, drill out a single rivet and use that rivet hole for spraying that particular section. Don't forget to rivet it back after spraying to keep structural integrity.

Beside fresh water bathing regularly, (even shore-based) navy aircraft have enough holes on the underside, for proper drainage.

Champ

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