Detection of Stress Corrosion Cracking in a Dual-Phase Steel Using Electrochemical Noise and Impedance Spectroscopy

Abstract

An attempt has been made to detect the stress corrosion cracking (SCC) initiation and propagation of a dual-phase steel in 3.5% sodium chloride (NaCl) solution at different pH values (3 and 7) by using electrochemical noise (EN) and electrochemical impedance spectroscopy (EIS) techniques during slow strain rate tests. When the steel was immune to SCC, EN readings consisted of transients with high intensity and frequency, which did not change throughout the tests; Nyquist diagrams showed a single depressed capacitive-like semicircle; and Bode plots did not show the presence of a protective layer. On the other hand, when the steel was susceptible to SCC, current-noise-time series consisted of transients that increased in intensity and frequency at the yielding point but decreased toward the final fracture; Nyquist diagrams indicated a process controlled by diffusion of aggressive ions through a corrosion products layer; and Bode plots showed evidence of the existence of a protective layer.