Do you have to prime in between parts?

[Battson]

Hi everyone,

I am looking for some wisdom, from experienced builders:

When you assemble alloy wing parts (say 2024-T3 for instance), is it important that all parts which are permenantly afixed together receive primer between them. My example is the spar cap strips and spar C-section. Will priming over the assembed spar give the same (and adequate) protection against intra-spar corrosion, compared to painting the parts seperately then assembling them?

I am no expert, but see advantages and disadvantages each way:

• Priming individual parts gives protection to the surfaces in contact, but increases weight, and permanent fixtures (e.g. rivets after priming) introduce unprimed ingress points for corrosion.
• Priming the assembled spar provides a single unbroken layer of protection, in theory, but leaves the internal mating surfaces exposed and in contact with each other, and corrosion could develop in there.

Maybe I'm making too big a deal about this, I understand some people in dry climates consider priming the interior of wings "optional". Any comment? Either way, I live in a country where you're never too far from the sea.

I appreciate any wisdom, experience, or advice you can share. Thanks.

 

[wally]