Assessment of stress corrosion crack initiation and propagation in AISI type 316 stainless steel by electrochemical noise technique

Identification of damage evolution during SCC on 17-4 PH stainless steel by combining electrochemical noise and acoustic emission techniques

“…High resistance values have been observed during the first stage, while the second stage showed relatively low values and again increasing values, even if with high scatter, have been observed during this stage. Similar results have been reported by Anita et al [59] for AISI 316 SCC and related to three significant occurrences: a first stage with relatively high R N values corresponding to the completion of the pitting process and beginning of the crack initiation process and consequence of continuous dissolution and repassivation processes taking place. A second stage corresponding to the completion of the crack initiation process was characterized by low R N value and a second R N value peak during the last stage was attributed to completion of the crack propagation.…”

“…A first stage of low electrochemical activity characterized by low instantaneous charge and slowly growing cumulative charge up to about 1,500 s. After that a sudden increase in the electrochemical activity can be observed with a stepwise growth of the cumulative charge (stage II) and after a quiescence step at about 10,000 s a rapid increase of the cumulative charge (stage III) characterized by an ever growing electrochemical activity until final failure was observed. Similar trains of noise bursts have been observed at long time during SCC test of U-bend type 316 samples in boiling acidified NaCl solution [59].…”

“…The 1/f 2 slope is associated to the presence of a steep jump at the beginning of the transient, whatever the shape of the decaying part as well as transients characterized by ends with a rapid decrease after a slow increase [55]. During the first stage some spikes of roll-off slope to very low value, being associated to unstable surfaces where passivation and general corrosion processes alternate, were observed [59]. However correspondence between roll-off slope and the type of corrosion mechanism is not always confirmed and contradictory result have been reported by several authors [59] [60].…”

“…During the first stage some spikes of roll-off slope to very low value, being associated to unstable surfaces where passivation and general corrosion processes alternate, were observed [59]. However correspondence between roll-off slope and the type of corrosion mechanism is not always confirmed and contradictory result have been reported by several authors [59] [60].…”

Methodology for a mechano-electrochemical evaluation of the coupling at the crack tip. Application of halide-induced Stress Corrosion Cracking of Zircaloy-4

“…v ⁄ parameter estimation mainly consists of evaluating the dissolution current density j at the crack tip while da dt can be related to j by local Faraday's law [2]: (i) electrochemical noise measurements at the Open Circuit Potential (OCP), with the evaluation of the exchanged current density between the working electrode and an inert electrode; this method was successfully applied by several authors [6][7][8][9][10][11] to detect SCC initiation; yet, current fluctuations at the crack tip can turn out to be undetectable when the crack has propagated; (ii) galvanostatic polarization with difficulty in promoting crack tip dissolution toward pitting and ensuring the repassivation of crack the mouth during propagation; (iii) current density measurement under potentiostatic polarization over the depassivation potential at the crack tip.…”