Oxygen corrosion is a possible process in electrochemical corrosion, as it occurs with metals. The other possibility is that hydrogen corrosion is taking place. In this article, you can find out what happens chemically with oxygen corrosion and what requirements must be met for it.
Oxidation by oxygen
From a chemical point of view, oxygen corrosion is a redox process. Metals are oxidized by oxygen. The process only works if water or at least air humidity is available. In completely dry environments with dry air, oxygen corrosion cannot occur. Then there can be no rust.
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Oxidation with oxygen is chemically similar to combustion, but it takes place without generating heat. Oxygen corrosion is responsible for the formation of rust on ferrous metals.
The prerequisites are 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 even when exposed to air.
Course of the reaction
The reaction itself is an electrochemical process through the formation of a so-called galvanic cell. It consists of the two poles (cathode and anode) and the electrolyte solution, which together form a type of battery. This battery is what drives 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 becomes negatively charged. That is the reduction reaction. In the next step, the metal is then oxidized. That is the oxidation reaction.
At the end of the reaction, more and more iron is converted into FeOOH, i.e. iron oxide hydroxide, which we know as rust. The process continues as long as there is water and oxygen. That is why rust cannot be stopped.
Oxygen corrosion in copper
When copper oxidizes to verdigris, there is a similar reaction. However, the oxide layer that forms copper is stable and corrosion can therefore no longer proceed after the typical greenish patina of copper has formed. Since other substances are involved in addition to oxygen and water, the oxidation of copper cannot be referred to as pure oxygen corrosion.Tips & Tricks Rust converters convert the FeOOH back into a stable compound, namely iron phosphate.