Potential and Strain rate Impact on the Electrochemical Properties of 304l Stainless Steel Under tensile Stresses

The majority of this work was to find out if Dynamic Electrochemical Impedance Spectroscopy can be applied for non-stationary electrochemical processes examination, such as the instantaneous changes during the passive layer cracking. Characterization of the passive layer cracking dynamics is very important from the diagnostics point of view. Especially, if investigated materials are protected by passive films exposed to substantial loads. Presented paper proves that the Dynamic Electrochemical Impedance Spectroscopy allows the determination of instantaneous impedance changes during the initiation stage of the SCC process, which is related to the crack of passive layer. Moreover, mentioned procedure makes possible prediction of the passive layer rupture under tensile stresses. Instantaneous impedance spectra for 304L stainless steel specimens in 0.5 M NaCl solution at room temperature were recorded. Measurements were conducted for different potential values and various strain rates according to the double-factor impact - electrochemical and mechanical. Impedance spectra have been depicted in the 3D diagrams illustrating system's impedance evolution over time. Each spectrum refers to 0.6 second of process duration, so reflecting the changes in the investigated system dynamics.