Hello Phil
Straight from the mfg. Zinc Chromate needs a top coat to be most
effective. I know plenty of folk use it, it is however porous. Self etch
zinc chromate uses up half of its magic to neutralize acid.
Chemicals with acid and plating work OK but a pain to do.
My favorite corrosion protect ant is PPG DPLF! It is a 2 part epoxy
primer, it does not let in moisture. If you scuff surface it sticks better
than any paint I have tried. Works on aluminium, steel and fiberglass.
Downright amazing. It does not have UV inhibitors though.
When I do Mod 72, I will paint both ID and OD with DPLF,and assemble wet.
When I made precision pins for tailplane torque tube, I used wet paint as
an assembly lube, and coated the ID of the TT as well.
Painting bare fiberglass, DPLF thin and let it full cure before applying
top coat or K-36 high build primer. Adhesion is great.
One word of advise, if you are going over self etch primer with DPLF you
need to wait till it is full dry. Whatever the mfg says, I find it takes a
lot longer. If you put DPLF over slight not dried self etch, or slight not
dried solvent, it will not allow the solvents to permiate. It will not
adhere as well as it has ability to do. If you take a razor blade or sharp
scraper and can peel off the DPLF, smell sample, if you detect solvent,
you didn't wait long enough.
I poured hot linseed oil inside aluminium and steel tubes and poured out
after coating and sealed things up.
Ron P.
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