MadSci Network: Physics

Re: would rust affect the stregth of a magnet

Date: Wed Feb 21 12:34:47 2001
Posted By: Ronald Fisch, Physics, Washington University
Area of science: Physics
ID: 982722352.Ph

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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