I used to install the Rust Evader units many years ago. Total useless crap. I tried to talk people out of them, which pissed off the parts and sales guys.There was no sacrificial anode, with the rust prevention purported to come from a slight electrical charge generated by two boxes hooked to the inner front fenders. But the customers had the satisfaction of opening the hood and looking at a blinking light on the control box, confident that it was keeping their Hyundai Excels from disintegrating in the NY road salt.