Jim Warman wrote:

> Given the more moderate temps in these areas, the weather rarely gets cold
> enough to keep the salt from "working". At -30C, salt approaches an "inert"
> condition and can no longer work it's "magic".

Actually, getting below the freezing point of water with NaCl (salt) in
it is what happens. This is around 15º F or about -10º C. Maybe
you're thinking of CaCl2 'salt' that has a much lower freezing point in
water solution. It's what's used inside tractor tires for this reason.

> An Alberta car that is parked outside all winter will usually take a while
> to rust.... Parked in a very warm garage, the salt laden snow will fall from
> the chassis farily quickly and it will take a while to rust.... Parked in a
> "cool" garage, the snow and ice can remain packed around chassis components
> at a temperature warm enough for the salt to "work".

Well, the main factors here are salt and *liquid* water together on a
ferrous surface. Solid water (ice) will not cause rusting nor will dry
salt. Remember, though, that dry salt is hygroscopic. It will combine
with water vapor in the air. If there is essentially none available
because of the cold, it stays dry and harmless. In the first case, you
may be accelerating rusting because you're getting the car warm enough
to produce liquid water where it might remain dry outside. Sitting
outside depends mostly on the ambient temperature and humidity. The
last scenario is probably the worst of the three.
--
C.R. Krieger
(BMW driving enthusiast)