Eddy current technique as a nondestructive method for evaluating the degree of sensitization of 304 stainless steel

• Published in: Corrosion science 2020-08, Vol.173, p.108742, Article 108742
• Main Authors: Kelidari, Yeganeh, Kashefi, Mehrdad, Mirjalili, Mostafa, Seyedi, Mahla, Krause, Thomas W.
• Format: Article
• Language: English
• Subjects: Activation; Austenitic stainless steels; Degree of sensitization (DOS); Eddy current technique (ECT); Eddy currents; Electrochemical potentiodynamic reactivation (DL-EPR); Intergranular corrosion; Intergranular corrosion (IGC); Nondestructive testing; Stainless steel
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2020.108742

•Using DL-EPR to evaluate %DOS of 304 SS sensitized in different conditions.•Characterizing the microstructure of sensitized samples.•Using eddy current technique to establish the relation between %DOS and ECT results.•Developing the equation of % DOS = 2×10-5(EC Voltage)2 −0.1031 (EC Voltage) + 120.95.•Developing the equation of % DOS = 178.48 (N.I.) + 177.01 between impedance and %DOS. The application of eddy current (EC) technique in detection of sensitization before the occurrence of intergranular corrosion was investigated. For this purpose, EC experiments were performed on 304 stainless-steels sensitized at 650 °C and 750 °C for 1–20 hours. The double-loop electrochemical potentiodynamic reactivation (DL-EPR) and microstructural investigations were also carried out to evaluate the degree of sensitization (DOS). The DL-EPR results showed that the maximum sensitivity occurred within 4 h at 650 °C. The EC results indicated a reduction in voltage and impedance with increasing DOS. Finally, empirical relationships between DL-EPR and EC test results were developed.