The characterization of damage in SCC by an electrochemical impedance and statistical study of multiple cracking

To build a realistic predictive model, it is essential to understand how the damage is developed. The evolution of this damage on 304L steel in Scheil reagent during slow strain rate tests has been studied for 4 various strain rates. An observation of the distribution of crack traces (number, size and morphology) has shown that the damage is closely linked to the strain rate. Interrupted CERTs have been realised for two strain rates. For each strain rate, electrochemical impedance measurements at fixed frequency (100 mHz) and histograms of the distribution of the crack traces have been carried out. The linked use of two techniques to characterize the damage in stress corrosion studies gives very interesting results. The evolution of the phase of the electrochemical impedance is closely linked to the initiation rate of cracks. Density of cracks that have reached a given size could be a new definition of the critical damage in stress corrosion studies when multiple cracks exist.