Found this on wiki:
Sodium chloride road salt costs less than $50 per ton to produce but is corrosive to metals in highway structures and increases the concentration of sodium in drinking water which can lead to adverse health effects. Alternative deicing substances have been sought to alleviate these problems. CMA has been found to be an effective deicer and environmentally benign, though its production cost of $650 per ton is much greater than the cost of road salt. Using estimates based on New York State Data, a 1992 report in the Journal of Policy Analysis and Management concluded that $615 per ton would be saved in vehicle corrosion and that $75 per ton would be saved in aesthetic damage to roadside trees if the state highway agencies switched to using CMA as a deicer instead of sodium chloride rock salt, far outweighing its initial production cost. The report also warned that excessive federal subsidization of CMA could encourage its inefficient overuse.
If its "as" corrosive as tap water then you're fine. We wash our cars often enough anyways and you "washing" it off would essentially cause the same effect.