Reactivation Purpose

The Reactivation technique is more properly called Electrochemical Potentiokinetic Reactivation, or EPR. It is used to evaluate the degree of sensitization to intergranular stress-corrosion cracking in austenitic stainless steels. The sensitization is the result of carbide precipitation at grain boundaries in heat-affected areas near welds. The carbide precipitation results in excess charge recorded during a cathodic-going scan of a passivated specimen. The maximum current observed on this cathodic scan divided by the sample area is a quantitative measure of the degree of sensitization. For the highest accuracy results, the maximum current is normalized to the area of the grain boundaries found microscopically.

For details on the EPR method, consult Majidi and Streicher, "Nondestructive Electrochemical Tests for Detecting Sensitization in ANSI 304 and 304L Stainless Steels", in Electrochemical Techniques for Corrosion Engineering, R. Baboian, ed., NACE, Houston, TX, 1986 and references therein. The DC Corrosion Reactivation technique corresponds to the Simple EPR technique. To perform the Double Loop EPR technique, you must correctly set up a Cyclic Polarization experiment. The Single Loop EPR test can be performed by proper selection of parameters in the Reactivation Technique. Select equal activation and passivation potentials, and select either an activation time or a passivation time of zero.