Hello,

My cracked spinner just came back from the repair station looking
beautiful, and with a yellow tag attached. Time to paint it...

The process used to be:

* Clean the aluminum with "Alumiprep"
* Treat it with "Alodine"
* Paint it with a zinc-chromate epoxy primer.

OK, Alumiprep & Alodine are still available. But I hit a snag with the
primer. What I used to use was PPG DP40, which is a two-part primer
that
looks like baby puke and dries hard as a rock. DP40 contained zinc. Zinc
is important because it likes to corrode. Moisture attacking a zinc-treated
aluminum panel will prefer to corrode the zinc, and will leave the
aluminum alone.

DP-40 is alas gone. The new replacement DPLF-40 is still the proper
bilious green, but contains no zinc. The can proclaims "No Chrome!".
The
bilious green is apparently attained with useless pigments.

A cursory web search did not reveal any source of zinc-chromate epoxy
primer. It seems to have been regulated out of the market.
Zinc-chromate
lacquer primer is still available.

If this was an interior part, I wouldn't worry about it much - just prime
with zinc chromate. But the spinner is in front of the airplane turning
2500RPM and being blasted by 125MPH winds. Mechanical strength is
important.

Looks like I might have to just punt and use the DPLF40 ( actually,
DPLF48,which is white ) and depend on the alodining and the superior
sealing properties of the epoxy primer to keep the aluminum from
corroding.

Comments?

- Jerry Kaidor ( jerry@tr2.com )




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