If anyone didnt realise its bad for your car......Taken from DW.
Although dry salt is inert 15 – 20.oF (9 – 29.oC) is considered the lower limit for salt to melt snow and ice but once H2O, even in the form of moist air (i.e. humidity) is added the freezing point is lowered and the sprayed brine solution used on roads will have an adverse effect (the formation of rust and/or corrosion) on the vehicles paint and undercarriage. When washing the vehicle ensure that all salt removed to avoid a brine solution remaining on the paint finish. Using a durable protection (Collinite Insulator Wax) will provide a sacrificial and renewable protection to the vehicles paint finish.
The salts (salt CI and water H2O produce oxides, which cause corrosion) used for freezing point depression in a sprayed brine solution (often mixed with grit / sand for tyre adhesion) commonly used are;
(a) Sodium chloride (NaCl) the most common salt used Sodium chloride (rock salt, halite) lowest practical temp: 15.oF (9°.C) keeps sidewalks dry, corrosive, damages to concrete and vegetation
(b) Calcium chloride (CaCl2) works at lower temperatures than sodium chloride. Lowest practical temp: 20.o F (29. °C) melts ice faster than sodium chloride, attracts moisture, surfaces slippery below
(c) Magnesium chloride (MgCl2) is the name for the chemical compounds and its various hydrates MgCl2 (H2O) x. These salts are typical ionic halides, being highly soluble in water. Melts ice faster than sodium chloride. Lowest practical temp: 5. °F (15°.C) attracts moisture
Magnesium chloride is very effective even at the lowest temperatures but also contains the most aggressive corrosives (especially on glass surfaces) and a sprayed brine solution, it is used to prevent snow / ice adhesion to the road surface. A number of state highway departments throughout the United States have decreased the use of rock salt and sand on roadways and have increased the use of solutions of magnesium chloride (often called "liquid magnesium chloride") as a de-icer. Magnesium chloride is much less toxic to plant life surrounding highways and airports, and is less corrosive to concrete and steel (and other iron alloys) than sodium chloride.
Anti-icing liquids, which according to State authorities, the liquid solution consists of - Magnesium chloride (MgCl2) Calcium chloride (CaCl2) and other liquids that work like anti-freeze, by lowering the freezing temperature of water and preventing ice from forming a strong bond to the road
[: Water has a low electrical conductivity, but this increases significantly with the dissolution of a small amount of ionic material such as sodium chloride. Sodium chloride CI and water H2O produce oxides, which in turn cause corrosion] 
Rust (Oxidation) [:electrochemical oxidation of metals in reaction with an oxidant such as oxygen] 
Needless to state a sprayed brine solution is corrosive; so once you've removed the ice / snow it may be advisable to remove the residue and apply a protective coating, especially on the undercarriage and suspension. Once heat is added to the brine solution (i.e. parked in a heated garage) like any chemical attacking a surface, temperature will dictate reactivity (acceleration of a chemical reaction by a catalyst [moisture and heat].