1995 Volume 44 Issue 3 Pages 183-191
The electrode potential, which plays an important role in corrosion, may be defined by either the electronic or the ionic energy level in the electrode. The electronic electrode potential corresponds to the real potential of electron, i.e. the real free energy for electron transfer from the point at the outer potential of aqueous solution to the point inside the electrode, which is found to be a linear function of the electrode interfacial potential difference. Under equilibrium condition, the electronic potential represents the Fremi level of equilibrium redox electron in the solution for electron transfer electrodes, and the hypothetical Fermi level associated with ion transfer equilibrium for ion transfer electrodes. With localized corrosion, the corrosion potential at the cathode site is more positive than that at the anode site. This corrosion potential difference does not correspond to any local difference in the Fermi level inside the corroding metal, but to the difference in the electrode interfacial potential difference at the two sites.