If the charging current is negligible, in the case of a single electrode reaction, the electrode current density () of the electric current flowing through the electrode is related to the flux density of a species B by the equation:
where is the normal component of the vector at the electrode-solution interface, is the charge number of the electrode reaction and is the stoichiometric number of species B. The ratio is to be taken as positive if the species B is consumed in a cathodic reaction or produced in an anodic reaction. Otherwise it is to be taken as negative. With the convention that the normal distance vector points into the electrolytic solution, a cathodic current is then negative, an anodic current positive.
PAC, 1981, 53, 1827 (Nomenclature for transport phenomena in electrolytic systems) on page 1835