I know the underbody is the battery cover but does anyone know what it is made of? With winter around the corner the salt trucks will be out soon. I don't want to take my Model S through a car wash but during the winter time I would like to clean the underbody of all the salt. I was wondering how the the underbody will withstand the salt exposure? Has anyone had an issues with washing the underbody through the car wash? And yes will move to the south as soon as I can so I don't have to worry about this problem!