|MadSci Network: Physics|
Rust is an oxide of iron, whose chemical formula is Fe2O3. Fe2O3, called hematite, is not magnetic. Therefore, if a magnet rusts, it is becoming weaker, because some of the magnetic material has been converted into nonmagnetic material. If you remove the rust by scraping it off the magnet, the magnet will not become stronger. However, removing the rust may allow the magnet to stick better to iron or other magnetic materials. This is because when there is no rust to get in the way, the rest of the magnet can make better contact with the other object that you want it to stick to. If you wanted to restore the magnet to the strength it had before it rusted, you would need to convert the rust back into a magnetic form of iron. Magnetic forms of iron include pure metallic iron, many kinds of steel (which is an alloy of iron and carbon, and usually includes various other elements), and also Fe3O4. Fe3O4 is a magnetic iron oxide, called magnetite. There are also lots of magnetic materials which are not made of iron.
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