Do new vehicles still need to be protected against corrosion? In Michigan, yes. The state of Michigan uses 22 tons of salt per linear mile in the winter. The also spray liquid brine (salt) on all the overpasses. This salt causes corrosion to start in the first year.
Car manufactures have come a long way in building vehicles that last but as long as they use metal, salt will cause the vehicle to rust. Car manufactures are not going to change the way they make cars for the few states (see our salt map on our website) that still use salt.