It is known that, in addition to corrosion processes, the electrochemical noise (EN) can be generated by some other disturbances such as mass transfer and flow turbulence. In this study the influence of both laminar and turbulent flow on the characteristics of electrochemical noise (EN) has been studied using a carbon steel rotating cylinder electrode (RCE) in aerated neutral (pH=7) 0.1 M NaCl and 0.1 M NaCl+0.1 M NaNO2 solutions. The RCE has a set of four graphite brushes for electrical connection. The supplied cathodic current was applied through the top two graphite brushes and measured the specimen potential through the bottom two to eliminate any expected cyclic variations in the measured potential.Prior to the measurement of EN, calibration of the mass transport properties of the electrode was performed by measuring the limiting current density for oxygen reduction as a function of rotation speed in order to estimate the transition from laminar to turbulent flow regime. EN experiments have been performed in free corrosion conditions (uninhibited and inhibited solutions), and with applied cathodic polarisation in the regions of hydrogen evolution and oxygen reduction processes. In the case of oxygen reduction and hydrogen evolution cathodic reactions it has been found that laminar flow had a negligible effect on the noise produced but a significant increase in the amplitude of the noise was observed in turbulent flow. On the other hand in free corrosion conditions in uninhibited solution the influence of flow was relatively insignificant and that was attributed to the low impedance of the corroding electrode. It is claimed that flow has a negligible effect in inhibited solutions due to the passivity of the system, which is responsible for the low rate of both anodic and cathodic reactions. Finally spectral analysis showed that the noise produced by turbulent flow had power at significantly higher frequencies than is normal for corrosion-related noise.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:518811 |
| Date | January 2010 |
| Creators | Shaglouf, Mukhtar Mohamed A. |
| Contributors | Cottis, Robert |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/effect-of-flow-on-electrochemical-noise-generation(580f04c4-74a1-4b8d-8662-0ebce9166818).html |
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