[TowerTalk] USTower anchor bolts rusting
patrick_g at windstream.net
Sat Apr 1 08:59:49 EDT 2017
There are paints formulated to go on over light rust, chemically modify
the rust, and form a long lasting paint coating. No primer needed or
recommended. I painted some light to moderately rusted (no flakey stuff)
4x4 inch square steel tubes 12 ft long that are exposed to the weather
and sun (south side of house.) These are columns to hold up a poured
concrete porch floor of the floor above. I painted them with
Rustoleum's version of this kind of paint back in '03-'04 era when
building our house and they still look like new and have no rust.
This paint was procured at Lowes but should be widely available. It was
available in spray cans and in quarts. I have only seen it on the shelf
in two choices of color; silver and black. I wanted another color for
some gates and fence stretch fixtures but when I talked to the Rustoleum
factory the minimum quantity for a "custom" color was way beyond my
needs so I had the Lowes paint folks use some silver as a base and added
green pigment. On a scale of 1..10 I'd give the experiment a 6.
I can highly recommend both the silver and the black but trying to use
silver as a base for a custom color is iffy. You could always paint over
the silver or black with paint of your desired color without harming
the rust handling/prevention.
I have never used this paint on aluminum and suspect it could be a bad
idea but on iron or steel with or without surface rust it has lasted
very well indeed.
On 4/1/2017 2:58 AM, Donald Chester wrote:
>> Grant KZ1W wrote:
>> Another fix I use is spray zinc "cold" galvanizing as I had to machine
>> some custom steel spacers under the base plate for leveling.
> Something I have found that works better than "Cold-Galv" is ordinary aluminium paint, Rustoleum or similar brands. I have found that after a couple of years rust spots begin to appear through the Cold-Galv, but it takes many years for aluminium paint to rust through, and it adheres to the metal rarely scaling. I put my tower up in 1981, using a base insulator I inherited from a fallen broadcast tower. The end castings were un-galvanised cast steel, covered with a mixture of rust and red paint. I stripped off the paint and sanded off the rust, then gave them a couple of coats of aluminium paint. I've had to re-paint it once in the past 36 years the tower has been up. The hot-dipped galvanising on the tower shows more rust spots than the aluminium-painted base insulator castings.
> I touched up the freshly cut ends of some galvanised steel straps I used in another antenna construction project using aluminium paint, and still no rust after several years. The paint blends in so well with the galvanising that you would think the whole thing was hot-dipped after it was cut.
> You don't have to remove all the surface rust, just the thick or loose scaly stuff. A thin coat of rust that is still firmly adhered to the metal soaks up the paint like a sponge soaks up water, and actually makes it adhere better. A technique sometimes used for painting steel with any kind of paint, is to brush or spray on a weak acid solution first. After the solution is thoroughly dry, paint is applied. The thin layer of corrosion helps hold the paint on.
> Don k4kyv
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