I have found that Rustoleum paints are tough and really hold up well if
enough is applied. Either spray cans or spray gun applied. For bare or
HR steel, I start with a coat of red primer, then a coat of grey primer
so holidays are visible, then two coats of the finish color, usually
yellow for equipment. I have several things (trailer, fork lift boom,
man basket, etc) that have been outside 8 years in CA and 5 years in WA
with no general rust, only small spots where they were chipped. Big box
and Krylon brands don't cover anywhere as well or last as long. Powder
coated stuff I've bought, once it starts to rust, makes a flaky mess.
RE phosphate conversions prior to painting - an very good way to prepare
bare steel, but a bit messy by hand. I was involved in salt spray
tests of painted electronic cabinets and the phosphating made a huge
improvement in durability. Just as chromate/Iridine/Alodine conversion
coating was our practice for bare aluminum.
I haven't tried aluminum paint in some time. Certainly a lot cheaper
than cold galvanizing.
Grant KZ1W
On 4/1/2017 0:58 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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