Around here, they call that fluid film.
They spray it all over the underside of the car, sometimes even in the engine compartment.
It is usually applied every year.
It makes it a nightmare to work on. You get absolutely slimed working on these. PITA.
And, before it is worked on, guess what? All of that fluid film is being cleaned off that and the surrounding area.
Here is an idea, quit putting salt on the roads! Yes, keep plowing and sanding. Just stop with the salt.
Salt destroys hundreds of thousands of dollars worth of cars/trucks and parts every year.
If a vehicle is rotted away in 10 years, then something is wrong.
Instead of buying another vehicle every 10 years for thousands of dollars, why not spend one thousand every 4 years for studded snow tires instead, hell, half the vehicles already have studded snows.
End rant.