Periodic table

Corrosion engineering consultant

Corrosion Doctors site map

Alphabetical index of the Corrosion Doctors Web site

Rust Spot

A rust spot pretending to be the Sun, our source of life and energy

Pale Rust on Darker Rust

(Courtesy of Kingston Technical Software)

Rust Colors

Only Iron and steel rust. Other metals corrode. Rusting is an oxidation process. What we normally call rust is a flaky red-brown solid which is largely hydrated iron.The primary corrosion product of iron is Fe(OH)2 (or more likely FeO.nH2O), but the action of oxygen and water can yield other products having different colors:

  1. Fe2O3.H2O (hydrous ferrous oxide, sometimes written as Fe(OH)3) is the principal component of red-brown rust. It can form a mineral called hematite.

  2. Fe3O4.H2O ("hydrated magnetite" or ferrous ferrite, Fe2O3.FeO) is most often green but can be deep blue in the presence of organic complexants as shown here.

  3. Fe3O4 ("magnetite") is black