A New Electrochemical Potentiokinetic Reactivation Test for Determining Degree of Sensitization in Ferritic Stainless Steels

An electrochemical potentiokinetic reactivation (EPR) test has been developed for quantifying the degree of sensitization of ferritic stainless steels (SSs). This test is applicable to AISI430, 430 Ti, 430 Nb, 434,444, and 446. The test is conducted at 30 C in a deaerated 3 to 5 N H2SO4 solution. A test specimen is first passivated at + 400 mVSCE for 2 to 10 min, depending on the grade of SS, and then subjected to a reactivation step where the potential is decreased at a rate of 100 to 250 mV/min toward the open circuit potential (OCP) to determine whether a reactivation peak occurs. Results of the EPR test agree well with those of the Cu-CuSO4-50% H2SO4 immersion test.