Evaluation of passive film behaviour of super austenitic stainless steels at different potential regions using dynamic electrochemical impedance spectroscopy

Journal of Solid State Electrochemistry (Impact Factor: 2.23). 01/2010; 14(7):1197-1204. DOI: 10.1007/s10008-009-0948-5

ABSTRACT Potentiodynamic anodic polarisation and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out
on 316L stainless steel and alloys 926 and 31 in natural seawater in order to assess the crevice corrosion resistance. DEIS
measurements were performed over a wide range of potentials covering the corrosion potential, passive region, breakdown region
and dissolution region. The impedance measurements in potentiodynamic conditions clearly reveal the changes that occur in
the passive layer with change in potential. The impedance spectra at different potential regions were also discussed elaborately.
The surface morphology of the alloy after crevice corrosion was studied using optical microscope and atomic force microscopy.

KeywordsStainless steel-Crevice corrosion-Dynamic electrochemical impedance spectroscopy-Atomic force microscopy

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    ABSTRACT: Effects of applied potential on stable pitting corrosion of 304 stainless steel were studied by potentiostatic polarization and three-dimensional video microscope. The results showed that pit mouth morphologies and three-dimensional structures were dependent on potential. Higher potentials resulted in more open pits. Pit volume, depth, and width increased with potential. The ratio of pit depth to width continuously changed with time and potential. The pitting current density of a single pit increased with potential, indicating that an ohmic potential drop presented between the pit internal surface and the bulk solution, but stable propagation was still controlled by corrosion products diffusion.