[TowerTalk] Experience with Sacrificial Zinc?

[M?ximo EA1DDO_HK1H]

I can see Rust-Oleum sells Urethane Aliphatic enamel:

https://www.rustoleum.com/product-catalog/industrial-brands/commercial/urethane-coatings/3300-system-acrylic-aliphatic-urethane-coating

73, Maximo

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Donald Chester
Sent: martes, 10 de agosto de 2021 18:18
To: towertalk at contesting.com
Subject: [TowerTalk] Experience with Sacrificial Zinc?

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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