plates are used on boat motors and such as well.... Having an '08 MB E class, there is no rust anywhere, and it is a daily driver.... keeping her clean and keeping those little crevices cleaned out along the fender wells and rockers will help....you have get down under there to see those.... The big rig gets sprayed off every evening in our wash bay before getting parked in it's new heated floor truck garage. Finally the company I work for is given in to my wishes....lol
I might add, the only proven rust device I know of is YOU....good luck