Howdy,
Gerry Bay and Pat Barthelow asked similar questions about using silicone
for sealing antenna components.
I know I posted some drivel about this in the past. An archive search
might produce the information. It probably appears under the heading of
putting GOO on antennas.
Don't use hardware store types of silicone on aluminum antennas!!!!!!!
1) Aluminum is a very reactive material.
2) Almost all one part (doesn't require measuring and mixing) silicones
cure via a chemical reaction relying on moisture and the silicone to
create acetic acid. That's why your nose burns and your eyes water!!!
The acetic acid attacks the aluminum and oxidizes it. So, the one part
silicone ends up trying to attach itself to an oxidized surface. This
just doesn't work! The oxide prohibits a good bond and the silicone
separates from the aluminum in a very short time.
I'll bet that every TT subscriber, that has done this can verify that
later they observed that the silicone didn't stick to the aluminum.
If you must use silicone, go to an industrial supplier and ask for the
most expensive, aerospace grade of "one part" silicones, designed for
use with sensitive electrical circuits. This stuff uses a different
(non-acidic chemistry) that won't attack the aluminum as much. It just
takes about a week to fully cure.
If you're like me and don't need anymore headaches, go get a big tube of
the 20-30 year latex caulking compounds, at real cheap prices. Or, use
3M Scothkote and good vinyl electrical tape like 33 or 88 (another post
in the archives).
Of course, bonding anything to anything with anything requires a few
simple fundamentals. 1) Clean everything to remove ALL oily substances
(Yes, even your own grubby, oily fingerprints!). Then scuff the mating
surfaces with fine sandpaper or Scotchbrite( better). Then remove all
the dust with a clean dry cloth. Then put your goo on it immediately.
A bare aluminum surface can oxidize enough to prevent a good bond within
1 hour in humid environments.
Bon Gooping!
73, Kurt
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