Have the CAT on my ute from new. This is the second one with 4 pads after original unit's housing cracked after10 years.
Nothing will prevent rust entirely but IMHO this helps slow it down.
I go to Fraser every year at least once but usually 2 or 3 times and the only rust I had was above windscreen after a dodgy installation of replacement windscreen.
Nothing replaces thorough cleaning after beach trips with several washes and sprinkler under vehicle also several times.