Rust

Rust is a collection of iron oxides and iron oxyhydroxides formed when iron corrodes in the presence of water and oxygen. Its porous, flaky structure usually fails to protect the underlying iron from further corrosion.

Iron corrosion: The deterioration of iron through chemical or electrochemical reactions with its environment. Rust is the solid product of iron corrosion in wet, oxygen-rich conditions.
Iron: A metallic chemical element with symbol Fe and atomic number 26. Rust forms through the oxidation of iron metal.
Corrosion protection: Methods that prevent or slow the chemical deterioration of materials. Rust prevention relies on barriers, altered electrochemistry, or more resistant materials.
Hematite: An iron oxide mineral with the formula Fe₂O₃. Hematite can occur among iron corrosion products, though rust is not a single pure mineral.
Atmospheric corrosion: Corrosion caused by exposure to air and its contaminants, often in the presence of moisture. Rust composition and growth depend strongly on humidity, pollutants, and wetting cycles.
Electrochemical corrosion: Material degradation driven by coupled oxidation and reduction reactions at an electrochemical interface. Rust formation separates iron oxidation from oxygen reduction across wet metal surfaces.
Water: A compound of hydrogen and oxygen with formula H₂O, liquid over a broad range of everyday temperatures. A thin water layer enables ion movement and electrochemical reactions on iron.
Galvanization: The application of a protective zinc coating to iron or steel. Zinc corrodes preferentially and can protect exposed iron at coating defects.
Magnetite: A magnetic iron oxide mineral with the formula Fe₃O₄. It can form in oxygen-poor regions beneath or within corrosion layers.
Chloride-induced corrosion: Corrosion accelerated or altered by chloride ions at a metal surface. Chlorides can change rust phases and undermine protective surface layers.

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