Electronic by far!! 1 of my old 4x4 mates was given a elect rust proofing device as a trial to convince all of his other 4x4 mates and basically the whole 4x4 club... And i was very very impressed!! Took it upto fraser and he sand blasted his goose neck and tow ball right back to raw metal and even sandblasted through some already rusty stuff. Now on the beach overnight youd think by the next morning it would be showing signs of rust. But nothing at all. He drove it into waves and wash/saltwater and a week later still on fraser and nothing (still shiney even). It doesnt stop the rust just slows it down drematically. And also doesnt mean you shouldnt get lazy and still wash out your chassi's and sandy spots and the usual (check breathers, and regrease everything). It worth every penny... BD