Re: OT: Bad paint

On Fri, 14 Sep 2007 22:01:49 -0700, "Paul Hovnanian P.E."
<paul@xxxxxxxxxxxxx> wrote:

I recently found an old Escort radar detector that had been sitting in a
desk drawer for quite a few years. It has a pretty substantial case,
made of cast aluminum with a textured dark gray finish. When I picked it
up, the paint was quite sticky to the touch. When I rubbed it, a surface
layer came off.

I have seen this happen to other equipment. After some years, the paint
gets soft, sticky and peels off. While the radar detector did spend
years in a hot (and cold) car, the other equipment has remained in
relatively benign environments.

What sorts of finishes are susceptible to this kind of breakdown

My guess is that it is an Alkyd enamel, and that the stickiness is not
from the basic Alkyd formulation but from the additives used to obtain
the hammertone effect combined with environmental factors such as UV
or ozone exposure. Is there an ozone emitting laser printer near
where it was stored? The peeling is due to inadequate surface
preparation or lack of the appropriate primer.

For nice looking project boxes that will hold up well try Krylon spray
paint with the appropriate surface prep and primer. I like the Krylon
Industrial direct to metal enamel (no primer required), alas not
available retail since retail users cannot be relied upon to have
sense enough to read the directions and use ventilation. AFIK all of
the Krylon spray paints have approx twice as much solids per fluid
ounce as the low end paints like Rustoleum and Painters Choice, which
combined with a superior spray nozzle which delivers a fan shaped
pattern instead of round means you can get a better finish with one
coat of Krylon than with two coats of Rustoleum, etc. There was a
time when % solids was printed on the can, but I think Rustoleum must
have paid off the right politicians as this important bit of info is
now missing. Not that you can't still readily see the difference when
applied, Rustoleum is still thin and runny compared to the much
thicker and less prone to running Krylon. For best long term
durability select an epoxy or polyurethane intended for outdoor use
from the manufacturers web site and then find out where to buy it
rather than limiting your options to what is stocked at the local
store, which will usually be very limited and not include any of the
better quality paints such as:

<http://krylon.com/main/product_template.cfm?levelid=5&sub_levelid=12&productid=1804&content=product_details>
.

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