Todd,
Not knowing what the building actually looks like, and material made of(alum. or galv.steel). Here's my ideas:
1. Clean with at least a 3000psi, 3.5 - 5 gpm pres.
washer.
Apply chlorine with a cleaner/surfactant added.
The key is to get contaminants off(mold,
mildew,grease, oil,)and if oxidized finish, as
much as possible of the loose paint finish(use
your hand test after it dries, if chalk is on
your palm of hand, do it again). We generally
use a 15 degree tip that brings our psi down to
around 1500 or so and allows full flow of water
(5.5 gpm.).
2. After allowing to dry out( overnite w/sun out),
if rust is showing( orange/reddish spots) treat
with phosphuric acid(read label, if you never
used). Wipe off acid residue, let those areas
dry.
3. If rust is a problem, apply a good grade oil
based(alkyd) stain/rust blocking primer/sealer.
At least 1 coat; if quite rusty, apply 2 coats.
I would apply with
a good grade airless paint sprayer(that can
handle .75 gpm or better) with a tip size of
about .315 - .417. Let this coat(s) dry min. 4
hrs; preferably overnite(12-24 hrs.)
4. Finally, apply a premium grade of a Direct To
Metal (DTM) 100% acrylic paint(satin finish at
least, maybe a s/gloss finish), in 2 coats with
4 hrs. min. drying in between coats. Try a .317
tip for generally spraying, and reduce size for
any intricate spray work.
Note: This spray work on a metal building does
require some skill, don't take this complete
job lightly, as you can end up
with "hoildays,dry areas, and drapes( runs) in
the finish.
Some areas of the country require application
of coatings and paints for hire, to be a
licensed painting contractor( requires taking a
test,bond, ins., etc.). Not trying to scare ya,
be careful!
If more questions on the painting end of job
(pricing, technique, etc.)
feel free to e-mail me, procoatpaint@juno.com;
or call 727-849-8191(after 6:00pm EST.)
Have Fun!
Ken
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