Electrochemical noise analysis of tribo-corrosion processes under steady-state friction regime

Tribocorrosion processes of austenitic stainless steel in an aggressive medium close to that used in pressurized water reactor nuclear plants have been investigated by electrochemical impedance and noise measurements. The experiments were carried out under steady-state friction regime yielded by the continuous circular displacement of a fretting probe against a large disk electrode. The current fluctuations generated by film removal and surface repassivation at the wear track and flowing to a small disk electrode inserted at the center of the large one and electrically isolated from it were measured with a zero-resistance ammeter (ZRA) connected between the two electrodes. This allowed the power spectral density of the current fluctuations to be estimated at the wear track. Results have shown that only a small part of the current lines flows to the central region connected by the ZRA. This was confirmed by finite-element-method simulations that also showed that the anodic effects progressively spread out of the wear track.