In this article the corrosion current, a fundamental parameter in corrosion research, is introduced.
What most scientists are interested in is the corrosion rate, meaning how fast the sample is destroyed. This depends on the corrosion current, so the amounts of electrons per time that are transferred inside the system.
In the example of the steel in an acid solution from the previous chapter this would be the electrons that are transferred from the steel to the protons to form hydrogen.
The knowledge of the corrosion current allows calculating the amount of material that is corroding per time unit. The corrosion current flows between the two reactions in the system, e.g. hydrogen evolution and steel oxidation, and can’t be measured directly. Both reactions must provide the same current, so they can exchange this current, i.e. all electrons donated by the steel need to be accepted by the protons to form hydrogen.
Donation and uptake of electrons happens at the corrosion potential as discussed in the previous chapter. This means the corrosion current is flowing at the corrosion potential and at the corrosion potential the electrons donated by the oxidation and the electrons accepted by the reduction are equal.