THE CHARACTERIZATION OF DAMAGE IN SCC BY AN ELECTROCHEMICAL IMPEDANCEAND STATISTICAL STUDY OF MULTIPLE CRACKING

To build a realistic predictive model, it is essential to understand h ow 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 tr aces (number, size and morphology) has shown that the damage is closel y linked to the strain rate. Interrupted CERTs have been realised for two strain rates. For each strain rate, electrochemical impedance meas urements at fixed frequency (100 mHz) and histograms of the distributi on of the crack traces have been carried out. The linked use of two te chniques to characterize the damage in stress corrosion studies gives very interesting results. The evolution of the phase of the electroche mical impedance is closely linked to the initiation rate of cracks. De nsity of cracks that have reached a given size could be a new definiti on of the critical damage in stress corrosion studies when multiple cr acks exist.