Color of Iron Oxide

Iron oxide is a reddish brown solid. Iron oxide, or iron trioxide, with the chemical formula Fe2O3, is the main component of rust and hematite. The main cause of rust is the reaction of iron metal with water and oxygen in the environment in the presence of impurity carbon, and the iron metal rusts.

Presence of ionic compounds and water: Iron metal rusts if it comes into contact with an aqueous solution with a high concentration of ions. This is because ionic compounds are electrolytes that promote the release of electrons from the metal, leading to rusting. For example, there are micro-droplets of seawater in offshore areas, and seawater contains sodium chloride, which is an ionic compound that causes rapid oxidation of ferrous metals. Even if there is only water, it will quickly adsorb acidic gases such as carbon dioxide from the air, accelerating oxidation. In addition, many stainless steels have good resistance to the formation of oxides through the formation of a protective oxide layer, but less resistance to the formation of chlorides.

Presence of acidic compounds: Factories emit acidic gases which rust ferrous metals. This is because acidic gases combine with moisture in the air to become electrolytes.

High temperature: Ferrous metals rust when the temperature is high.

Scratched or bumpy surfaces: Ferrous metals will rust if they are scratched or bumpy. This is because bumpy surfaces tend to accumulate electrons.

Contact with less reactive metals: If ferrous metal comes into contact with less reactive metals (such as tin and copper), it will rust.