The Potentiodynamic Polarization Scan
By D G Evans and L L Scribner
Keywords:
DC potentiodynamic polarization, corrosion, Nernst potentials, potentiostat, sensitization, Tafel equation, electrochemical potentiokinetic reactivation.
An overview of the potentiodynamic polarization scan is discussed with reference to real electrochemical systems such as the corrosion of stainless steel. The basic concepts of electrochemistry are introduced including anodic and cathodic polarization, examples of oxidation and reduction reactions and the theory behind thermodynamic (Nernst equation) and kinetic treatment (Tafel equation) of experimental data. In addition, experimental protocols are discussed including correct cell design, appropriate choice of reference couples and instrumentation.
Finally, the application of the potentiodynamic polarization technique is demonstrated in the analysis of the sensitization mechanism of 304 stainless steel. The concept of double loop electrochemical potentiokinetic reactivation mechanisms are discussed.