I've seen guys who have that on their cars here and have more rust than other vehicles without it. A friend of mine is a machinest / welder / metallugist says that there really is no way to completely stop rust, only slow it down. He told me to periodically spray LPS, WD40, or similar into the frame, cracks and crevices etc. and that would pretty much keep rust at bay and probably last beyond my lifetime.
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