On Sat, 7 Apr 2018 13:34:25 -0400, "Jim Wilkins"
wrote:

wrote in message
...
On Saturday, 7 April 2018 18:05:25 UTC+1, wrote:
I thought I was doing therightthing by coating my trailer with cold
galvenized paint, thinking it would look lke newish hot galvenize
shee finish. ? I am now faced with a dull unfinished look. what can
I re coat with to get something better.


Thanks to anybody that can advise

Gerald Hosking


Talk to an experienced clerk in a paint store. Automotive spray paint
didn't stay on cold galvanizing very well for me.

"Cold galvanizing" refers to several different materials. The common
one, from Rust-Oleum and others, is a reggular organic paint binder
with up to 95% zinc powder. It's the least protective because it
generally hresults in poor electrical contact among the zinc
particles. It's often recommended to top-coat it and I'd just check
with the company that made it for recommendations on preparing it for
a top coat.

Another material, one that I haven't seen for about ten years but
which was popular for a while for coating boat trailers, is two-part
epoxy paint with the same zinc powder. Top-coating epoxy is always
tricky. It develops an "amine blush" on the surface from the amine
curing agent. You can't sand it off; it just smears around. Acetone
won't help, nor will other paint thinners.

However, thankfully it's water soluble and the blush can easily be
washed off with soap or detergent and water. My favorite is TSP, for
the same reason that it's used for prepping walls for painting: it
doesn't leave a residue.

The third material is harder to get in ordinary consumer products but
it's the best, and you'll find it from commercial sources. It's
INORGANIC binder (usually ethyl silicate) with 90 - 95% zinc powder.
The reason it's best is that it has good electrical conductivity with
the surface and with the particles themselves. That's essential to get
a true "galvanizing" effect, which is a sacrificial electrolytic
phenomenon in which the zinc is the sacrificial anode.

If you happened to get that, you'd better check with the supplier
about coating it. It's the one that least needs top coating.

Whatever you use, keep stirring or shaking the hell out of it as you
use it, or you'll get wildly different percentages of zinc as you
spray, roll or brush.

--
Ed Huntress