What Is the Definition of Oxidized Metal?

How does oxidation take place?

Oxidation of steel
This surface of heavily oxidized iron is known as rust. Photo &copy Sami Sarkis

Metal oxidation takes place when an ionic chemical reaction occurs on a metal's surface while oxygen is present.The chemical process involves the movement of electrons from the metal to the oxygen molecules.Then, negative oxygen ions generate and enter the metal. This leads to the creation of an oxide surface. Oxidation is a form of metal corrosion.

When Does Oxidation Occur?

This chemical process can occur either in air or after metal is exposed to water or acids.

The most common example is the corrosion of steel, which is a transformation of the iron molecules on steel's surface into iron oxides, most often Fe2O3 and Fe3O4.

The official Nobel Prize website explains the process as follows:

"As the oxide layer grows, the rate of electron transfer decreases. The corrosion stops and the metal becomes passive. The oxidation process may continue, however, if the electrons succeed in entering the metal through cracks or impurities in the metal or if the oxide layer is dissolved."

If you've ever seen an old, rusted car or rusted pieces of metal scraps, you've seen oxidation at work.

Which Metals Resist Oxidation?

Noble metals, such as platinum or gold, resist oxidation in their natural state. Other such metals include ruthenium, rhodium, palladium, silver, osmium and iridium. Many corrosion-resistant alloys have been invented by man, such as stainless steels and brass.

While one would think that all metals that resist oxidation would be deemed noble metals, that's not the case. Titanium, niobium, and tantalum all resist corrosion, but they're not classified as noble metals. In fact, not all branches of science agree on the definition of noble metals. Chemistry is more generous with its definition of noble metals than physics, which has a more limited definition.


Metals that resist oxidation are the opposite of the metals prone to it, known as the base metals. Examples of base metals include copper, lead, tin, aluminum, nickel, zinc, iron, steel, molybdenum, tungsten and other transitional metals. Brass and bronze, the alloys of these metals, are also classified as base metals.

The Effects of Corrosion

Preventing corrosion has become a lucrative industry. No one wants to drive in a rusted car if they can help it. But corrosion is more than just a cosmetic concern. Corrosion can be dangerous if it affects infrastructure such as buildings, bridges, sewage pipes, the water supply, ships and other vessels. Corrosion can cause infrastructure to weaken, putting lives at risk. So, while corrosion prevention may be costly, it is certainly necessary.