A Rust proof chassis

I have a suggestion for all
When purchasing a new lawn-mower, be it push, self-propelled, riding, etc., go to your local auto supply shop and pick up two or three cans of auto undercoating.Before putting gasoline or oil into the lawn mower, turn it over and spray the undercarriage with the undercoating. Let it dry, then apply a second coat ... and then a third... It is like a "tar" film, that completely covers the undercarriage and when cutting grass, rocks and other items that hit the undercarriage, do not chip away the paint.
I have done this to a lawn mower that I purchased over 12 years ago, and it has no rust on the chassis.

So, this is undercoating of the underside of the mowing deck.