Corrosion can only occurs, if the electrons donated by one reaction equal the electrons accepted by another system. For example, the electrons donated by an iron surface must be equal to the electrons accepted by the surrounding oxygen.
The electrons tranferred between these two systems define the corrosion current. Usually two electrochemical reaction (one reduction and one oxidation) have only one potential, where the current of both systems is equal. This potential is the corrosion potential Ecorr.
A simpler way to express the corrosion potential is: The corrosion potential is the potential where the corrosion current is flowing.
A corroding systems Open Circuit Potential (OCP) is usually the corrosion potential. This is why in the Corrosion Mode of PSTrace the OCP measurement is renamed to Ecorr measurement.
This section is a short explanation of the processes that lead to electrochemical potential and thus to corrosion processes. Most readers will have a rough idea of electrochemical potentials, noble and non-noble metals. However, a small recap of this knowledge seems suitable to understand the processes happening at the electrodes or corroding metals better. If …
In this chapter the Open Circuit Potential (OCP) and the Corrosion Potential are introduced. The principles of reference electrodes as well as the 0 V by convention potential of the standard hydrogen electrode (SHE) are explained. The electrochemical potential can be measured. Technically it is only possible to measure the difference in potential between two points. …