Electrochemical Characterization of the Stainless Steel Corrosion immersed in Seawater under Turbulent Flow conditions by Electrochemical Noise

Abstract

The electrochemical studies of the corrosion can provide indirect techniques that they can determinate the corrosion rate of metals or alloys immersed in a corrosive medium. For many years, most studies about the cathodic and anodic polarization behaviour of metals have been confined to traditional steady-state techniques, such as potentiodynamic sweep measurements. However, steady-state techniques are limited because they give information only on the ratedetermining step. Moreover, during the measuring process, technique such as potentiodynamic sweep polarize the electrode surface to such a great extent, in order to uncover corrosion mechanism, that the validity of the results can be questioned particularly in the cases when protective films. Transient electrochemical techniques such as Electrochemical Noise (EN), are less intrusive because they can provide information about the processes without disturbing the reactions with the voltage application.

Electrochemical Noise Study on Corrosion of Low Carbon Pipeline Steel in Sour Solutions

“…In the NACE brine, at 20 and 60 °C, and 0 h and 12 h, the LI showed a similar behaviour as the above described. This also suggests that the corrosion process is localised [7,[16][17][18]. At 24 h, the LI was close 1; these results allow proposing that the corrosion processes in both electrolytes could be regarded as localized nature.…”

“…is possible to see that the calculated LI in 3.5% NaCl at 20 and 60°C at the exposure time of 0 and 12 h, is 1; these values can suggest that, since the beginning of the experimentation to 12 h of the exposure time, the corrosion process is unstable, and therefore more likely to be stochastic. Then, according to different authors [7,[16][17][18], a localised corrosion process is likely to take place. At 24 h, the calculated LI was 1 at 20 °C and close to 1 at 60 °C.…”

“…Electrochemical Noise (EN) consisted of potential and current fluctuations spontaneously generated by corrosion processes recorded as a function of time [7][8][9][10][11][12][13]. According to Hladky and Dawson [14], the sources of EN may be classified in three categories: charge transfer effects, the noise related to surface processes occurring on the electrode and environmental changes.…”

Electrochemical Characterization of the Structural Metals Immersed in Natural Seawater: <i>In Situ</i> Measures

“…The study of corrosion metallic "in situ" (field measurements) is really important but it present a big and complex problem because in this study is necessary to include many parameters that in the laboratory is hard (some time impossible) to simulate; for example the exact oxygen and salts concentrations, temperature and pH variations. Although some limiting taking into the corrosion studies, the electrochemical techniques provides the necessary parameters to predict the useful life of the metals and alloys immersed in a corrosive medium, like natural seawater, with tests of short time [6]. Some of these electrochemical techniques are linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN).…”

“…It is important to mention that the spectral analysis method (done in the frequency domain) include the power spectrum analysis and the electrochemical noise impedance [6]; whereas the statistical method include (done in the time domain) median, standard deviation, electrochemical noise resistance (R n ), pitting index or localization index, transients analysis, etc. [10][11][12].…”