Establishing a New Solution Based on Hydrochloric Acid/Sodium Thiosulfate for Detecting and Measuring Degree of Sensitization of Stainless Steels Using Double-Loop Electrochemical Potentiodynamic Reactivation Method

In this study, a new solution based on hydrochloric acid (HCl) and sodium thiosulfate (Na2S2O3) has been developed for detecting and measuring degree of sensitization (DOS) using the double-loop electrochemical potentiodynamic reactivation (DL-EPR) method. Two types of stainless steels including Type 304 (UNS S30400) and 28Cr-33Ni-39Fe were sensitized at 650 degrees C for 10, 60, and 300 min. The results revealed that the new solution can detect sensitization in stainless steels suitably with higher resolution than previously reported solutions. The optimum acid concentrations were 0.1 M and 0.4 M HCl for Type 304 stainless steel and 28Cr-33Ni-39Fe, respectively. For Type 304 stainless steel, the depassivator concentration was 0.002 M Na2S2O3, while it was 0.001 M for 28Cr-33Ni-39Fe.