Use of Direct Current Resistivity Measurements to Assess AISI 304 Austenitic Stainless Steel Sensitization

This paper describes the feasibility of using direct current electrical resistivity measurements to evaluate AISI 304 austenitic stainless steel sensitization. ASTM A262 - Practice A and double loop electrochemical potentiodynamic reactivation (DL-EPR) tests were performed to assess the degree of sensitization (DoS) qualitatively and quantitatively, and electrical resistivity (ER) was measured by the four-point direct-current potential drop method. The results indicate that the DoS increases rapidly while the ER decreases gradually in response to increasing sensitization. Thereafter, the two parameters tend to remain approximately constant. This behavior may be due to the rapid increase in the volume fraction of M23C6 precipitates over a sensitization time of 4 to 6 hours, thereafter remaining relatively constant. The ER results, which were corroborated by other techniques used in this study, confirm the promising potential of this property to monitor the sensitization phenomenon in AISI 304 steel.