Hi Slomo,
This is so the "armchair" types do not get confused by your statement.
Magnetic Properties of Red vs. Orange Rust
Red rust (ferric oxide,
Fe₂O₃) and orange rust (often a hydrated form of Fe₂O₃, Fe₂O₃·nH₂O) are both
non‑magnetic in the everyday sense. While the pure iron in the original metal is ferromagnetic, the rusting process changes the iron into iron oxides, which have different atomic arrangements and weaker magnetic properties
Physics Van+1.
Why rust is not magnetic
When iron corrodes, it reacts with oxygen and water to form iron oxides. These compounds—especially Fe₂O₃—do not have the aligned magnetic domains that make pure iron strongly magnetic
Physics Van+1. In fact, Fe₂O₃ is often antiferromagnetic, meaning neighboring atomic magnetic moments align in opposite directions, canceling out most magnetism
Physics Van. Even hematite (a blackish mineral form of Fe₂O₃) is weakly magnetic, but ordinary orange/red rust is not strongly attracted to magnets.
Color and magnetism
- Red rust (Fe₂O₃) is the most common form and is non‑magnetic.
- Orange/yellow rust is usually a hydrated Fe₂O₃, which is also non‑magnetic and may be slightly less magnetic than pure Fe₂O₃ due to water molecules disrupting crystal structure Physics Van+1.
- Black rust (Fe₃O₄, magnetite) is an exception—it is ferromagnetic and can be attracted to magnets Physics Van+1.
Practical takeaway
If you test rust with a magnet, red or orange rust will not stick strongly, unlike magnetite (black rust). The color difference is due to the iron oxide’s chemical form and hydration, not its magnetic strength.
