Originally Posted by BroncoHauler
In the tank?
Aren't magnets ferrous metals? Don't ferrous metals rust?
If you have a steel tank, put the metal on the outside of the tank. For an aluminum tank , epoxy the magnet on the outside.
Well, many magnets are ceramic or chrome plated (the one I used was a chrome plated 1"x1" rare-earth), but my whole tank is just mild steel, and uncoated on the inside. You may get some rust above the fuel-line if it sits in a cold humid environment from condensation, but under-the fuel level it should be fine, and the magnet would have nothing to do with it. It is very common for oil-pans and differential covers to have magnets inside them, as do the gearboxes on most of my machine-tools.
I doubt a magnet on the outside would have sufficient magnetic flux passing through the tank to collect much, but perhaps. Just be aware that the moment the magnet falls off, you have all that stuff free to float about again.