How does oxygen corrosion work?

Oxygen corrosion is a potential process in the electrochemical corrosion found in metals. The other possibility is that hydrogen corrosion takes place. What happens chemically in the oxygen corrosion, and what conditions must be met, you can learn in this post.

Oxidation by oxygen

Oxygen corrosion is chemically a redox process. In this case, metals are oxidized by oxygen. The process only works if water or at least humidity is available. In completely dry dry air environments, oxygen corrosion can not occur. Then no rust can arise.

Oxidation with oxygen is chemically similar to combustion, but it occurs without heat generation. Oxygen corrosion is responsible for the formation of rust on ferrous metals.

The prerequisites are therefore only:

  • Presence of a ferrous metal
  • Presence of water or humidity
  • Presence of oxygen (in the air)

This makes it clear why untreated ferrous metals can rust very quickly in the air.

Sequence of the reaction

The reaction itself is an electrochemical process by forming a so-called galvanic cell. It consists of the two poles (cathode and anode) and the electrolyte solution, which together form a kind of battery. This battery is the driver of the reaction.

In the first step, the positively charged iron ions diffuse into the surrounding liquid. However, since the electrons remain in the iron, the surface charges up negatively. That's the reduction reaction. In the next step, the metal is then oxidized. That's the oxidation reaction.

At the end of the reaction, more and more iron is converted into FeOOH, iron oxide hydroxide, which we know as rust. The process progresses as long as water and oxygen are present. Therefore, rust is unstoppable.

Oxygen corrosion in copper

When copper oxidizes to verdigris, it is a comparable reaction. However, the oxide layer that forms copper is stable and therefore corrosion can not proceed after forming the typical greenish patina of copper. Since besides oxygen and water also other substances are involved, one can not speak in the oxidation of copper of pure oxygen corrosion.

Tips & Tricks

Rust converters convert the FeOOH back into a stable compound, namely iron phosphate.

Video Board: Rusting - Iron + water + oxygen = iron oxide