I am building a 750. I have the rudder and elevator finished. I have the right wing bottom skined,and am ready to rivit the top skin. I haven't been priming the parts or using corrosion protection. I live in the middle of Michigan and the plane will always be hangered at home. The only time it should get wet is when I wash it.  Now am wondering if I should be priming inside before I finish riviting. Any suggestions?


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At a minimum, apply corrosion protection to all the mating surfaces. For the parts that are already assembled you could spray the seams to get some protection at the interfaces of the parts.  If the protection is there from the start, you won't be worrrying about it later.


Oh Boy! There are as many corrosion protection schemes as there are builders!

Moi, I'm going for Alumiprep 33, Alodine, then Two pot strontium chromate Boeing BMS 10 -  standard Sherwin Williams epoxy primer. It will add about Six days to the build by my calculation and at most Twenty pounds if I use the full gallon can I bought ($429.00!). Probably use the equivalent of PRC 1422 polysulfide rubber sealer between dissimilar metals as well.

We have a saying about the weather here; "If you don't like it, wait Five minutes."

Now all I need is for someone to invent a hailstone proof primer...........



I used the Zenith recommended Cortec corrosion coating applied with a brush on all mating surfaces.  If is quite odor-less and easy to apply.  The remainder of the interior is bare.  In fact, the majority of my exterior is bare and polished.  After 4 years in a southern Ohio t-hanger, there are no aluminum skin corrision issues at all.  Bare steel where paint has rubbed off shows some signs of light corrosion only.   My hanger does have some humidity all year 'round as evidenced by some dampness on the concrete floors and any exposed paper gets wrinkled fairly quickly.  Nontheless, the bare aluminum is fine, but you should still coat those mating surfaces with a primer of your choice.


Good luck,



I live in Indiana and have decided not to use any corrosion protection. Just my choice. Not an opinion. I did ask a _______ represenative and they said I don't need it. Sorry about the blank. But I shouldn't say.

 I was also told not to worry about it. But when I started building the wings, I saw that there was a lot of area for water to enter the wing. I think I will Cortec from here out. I wonder if I just clean the seams that are already rivited and spray with Zinc Oxide primer without the etching process if that will somewhat protect it? I hate to get an acid product between the pieces that I cant get back out.


I used Cortec thinned with laquer thinner and applied by paint brush only between the mating surfaces of 6061-T6 aluminum... and it is a must between aluminum and steel surfaces. Corrosion will result if this proceedure is not followed regardless of where you live...except maybe in the Arizona desert.

Caleb told me to thin Cortec with water and it seems to work fine and still dry quickly, although he also said it's OK to rivet together mating surfaces with the Cortec still wet. I used distilled water, but I honestly don't remember if  Caleb said it had to be distilled or not!

You will be fine without any protection for what you describe.  I've seen 30 year old planes with no protection with no problems but at a minimum I like to see primer used on at least the mating surfaces. Bob is right it should be used between dissimilar surfaces.

The aluminum used by zen has excellent corrosion resistance.  I'm a believer in using a primer though...mostly because I plan to put my plane on floats.  I used zinc chromate and zinc oxide primer on all my surfaces. I bought a gallon of primer and a gallon of reducer.  I've used about 1/4 gallon and have primed everything so far except the wings.  I will be less than 1/2 gallon when I'm done.  It won't add more than a pound maybe two MAX on my build.

Do you apply the primer directly on the aluminum without any preperation, other than cleaning with a thinner or cleaner?  I understand completely the need to protect steel to aluminum connections.  We have aluminum dump trailers on our farm,and have a problem with salt from the roads. I figured I would use Cortec on those parts.



I use green scotchbrite or similar, then wipe with acetone. Acetone is also great to remove the part labels or any notes you write on the metal with a Sharpie.

Keep it light and do the mating surfaces only. As others have mentioned, 6061 has corrosion protection.



With so much corrosive elements all over our country and considering the effort and expense of building, I highly recommend an acid etch cleaner followed by alodine then epoxy primer on all parts inside and out.  The 6061 is one of the most corrosion resistant of all the aluminum alloys, but it will still corrode.  The few extra pounds is worth the peace of mind knowing any corrosion issues will be held to a minimum.


Steel parts should be phosphoric acid etched then epoxy primed then installed with a barrier film, including fasteners, to minimize disimilar metal corrosion.  3M marine sealant works well or some of the Pro-Seal products.


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