No. Not if you’re using a car normally. Water and salt will both cause corrosion and the longer salty water is in contact with the underbody of the car the faster corrosion will work. Even if you washed the underside of your car every evening after returning from work there would still be the corrosion from the eight or so hours since you left for work in the morning and that would accumulate.

If you are referring to a car wash, well the problem there is that car washes recycle their water. They filter out the dirt, but not the salt. So the salt water gets pressure fed into crack and crevices making things worse.

Not really, the best thing you can do is not expose the car to salt in the first place.

I once worked on an enthusiast's classic car back in the midwest which was exceptionally clean. The owner said every time he drove it in the winter or rain, which was rarely, he would put it in the air on the lift in his garage, and spray the car from below with WD-40 he purchased by the drum.

That seemed to have helped, but it's no panacea, and there's definitely rubber stuff which will be unhappy about getting WD-40 soaked regularly.

What about treatments like Dinitrol? These were quite popular decades ago in the Nordic countries.