I have a built in oversize three car garage that has finished walls a ceiling and all insulated. Even in the coldest winters (below zero temps) it stays above freezing out there and about 40 degrees is the coldest it gets with no additional heat.
I have a 220 electric heater that warms up the work bay nicely in short order and allows me to work in jeans a old t-shirt comfortably.
The heater is the beige item at the end of where one of the ceiling fan blades is. I totally rebuilt the entire suspension system on my 911 when there was a blizzard going on outside. My garage is also air conditioned for the hot summer months with a window unit.
The heater does not run much when I have it on.
Of course if the ice and snow melts, yea, the salt will attack faster. If it stays frozen I would think it is suspended.