john at kk9a.com john at kk9a.com wrote:
"Perhaps there is better paint, I used BriteZinc which is a zinc enriched
paint. It was a lot of work and still corrosion was winning the battle.
I am not sure what paint PJ4G uses but it is very very thick and it seems to
be holding up."
I had very poor outcome with zinc enriched paint. I painted over some rusty
spots on outdoor hardware years ago with stuff called "Cold Galv", and rust
began to peer through the paint in about a year. That paint is no substitute
for real galvanising, which works by *galvanic* action, meaning the zinc is in
direct electrical contact with the metal it is protecting. The zinc particles
suspended in enriched paint are insulated from the base metal by the body of
the paint, which if not a good insulator is at best a poor conductor.
I have found the most effective protective coating for rust-prone steel to be
Rustoleum aluminium paint. Aluminium paint protects not by galvanic action, but
by thin flakes of aluminium that effectively seal the base metal from the
outside elements. I use it on various parts of my tower and antenna hardware,
and achieve years of protection before re-coating. My tower has been up for
more than 40 years now, mounted on a base insulator salvaged from a fallen
broadcast tower. The steel castings at the top and bottom of the insulator
were un-galvanised. I painted them with one or two coats of aluminium paint
shortly after the tower was erected, and have re-painted them one time since,
probably 15-20 years ago, and right now only a very few minuscule rust spots
are peeking through.
Aluminium paint may not adhere well to freshly galvanised surfaces, but from my
experience, once the surface has weathered for several years, especially if
long enough for spots of rust to appear, aluminium paint adheres very well. It
worked well on a spot near the base of my tower where rain water dripping from
a copper open-wire feedline was causing the hot-dip zinc to deteriorate.
I find aluminium paint almost as effective as hot-dip galvanising, and *much*
more effective than the thin layer of electro-plated zinc on products sold at
local outlets like Ace Hardware and Rural King.
Don k4kyv
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