A cars underbody is most prone to corrosion. Underbody coating provides long term protection from corrosion to car's underbody. It also protects parts like internal body panels, frame rails and other inner cavities that are not physically accessible but are prone to corrosion.
The cavity wax protects the vehicle from moisture, dust, grime, and salt from the snow-clad roads. cavity wax is a process by which a waxy solution is sprayed inside the box sections of a car.