Effect of immersion time at the stainless steel 304L/NaCl (0.01 M) interface

Sa？etak Stainless steels are broadly used thanks to their specific physical properties such as their high corrosion resistance in poorly aggressive solutions. However, only few studies have been reported in the literature concerning their electrochemical behavior in low concentration electrolytes medium. Accordingly, the present work aims to study the immersion time influence on the solid-liquid interface properties of the austenitic stainless steel AISI 304L, immersed in a low-concentrated (0.01 M) sodium chloride (NaCl) solution. The electrochemical behavior of the interface was evaluated by electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) monitoring. The morphological features and the modification of the surface composition were evaluated by Optic Microscopy, Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometry, Atomic Force Microscopy, White Light Interferometry and X-ray Photoelectron Spectroscopy. It was determined by OCP measurement that the characteristic time of the interface stabilization is very long (several months). After an immersion of 2 months in NaCl solution, a second time constant on impedance phase diagram appears. Surface characterizations reveal a significant modification of the morphology and chemistry of the AISI 304L surface that can be linked to OCP/EIS observations. It can be noticed that the repeatability deviation of the EIS method was about 1 % while its reproducibility deviation was estimated to 35 %