Corrosion induces an electrical current,salt and water make a good electrolyte and thus increases the rate of corrosion.
When it's below freezing corrosion is slowed down but the salt/salt brines lower the freezing point and this along with the electrolytic qualities increase the rate of corrosion.
They've tried many methods to stop this process,in oceanliners they send an electrical current to "jam" the corrosion current and it's somewhat effective,this is used in cars also but it's not very effective because there are too many insulators that stop the current from flowing effectively.
The best solution is to use an oil type spray and apply it annually,all those wax base and tar base coating do is hide the rust and infact promote it by trapping moisture between the coatings.
If you live in an area where they salt the roads,the worse thing you can do is store the car inside in a warm area,this just speeds up the process.
YMMV.
