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Title: A study on the effects of solution concentration, surface finish and corrosion processes on electrochemical noise
Author: Hamzah, Khaidzir
ISNI:       0000 0004 2687 8110
Awarding Body: The University of Manchester
Current Institution: University of Manchester
Date of Award: 2009
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The aims of this research were to study the effects of electrolyte concentration, surface finish of samples and different types of corrosion on electrochemical noise. Basically, electrochemical noise is a term used to describe the spontaneous fluctuations of potential or current at electrode surfaces in electrochemical processes. In order to achieve the research aims, several experiments involving different corrosion systems were carried out. The corrosion systems were chosen to produce known types of corrosion. For the effects of varying electrolyte concentration on uniform corrosion, two systems were chosen; mild steel in hydrochloric acid, HCI and in sulfuric acid, H2S04 solutions. As for pitting corrosion, four systems were chosen, namely mild steel in a mixture of calcium hydroxide, Ca(OH)2 and sodium chloride, NaCI, mild steel in a mixture of sodium nitrite, NaN02 and NaCI, stainless steel 303 and stainless steel 304 in NaCI solution. Electrolyte concentration was varied in experiments involving the two former systems in order to see the effect of concentration on pitting corrosion. For the other two systems, the surface of the electrodes was varied to three finishes. 320. 600 and 1200 grit. This was to see the effect of surface finish on pitting corrosion. Analysis of the data obtained was carried out by examining the time records, the power spectra (including the impedance spectra). corrosion parameters (noise resistance, Rpo characteristic charge, q and characteristic frequency,ln, which were derived from simple statistical parameters). Maps of pairs of the corrosion parameters and the cumulative probability of each parameter occurring were plotted. Evolvement of corrosion parameters with time was also investigated. Analysis of the time record showed that they could distinguish uniform corrosion from pitting corrosion. From power spectra analysis, it was found that the technique could not be used to see the effects of changes in concentration and surfaces finish nor could it be used to distinguish uniform corrosion from pitting corrosion. It was found that parameter maps were not able to distinguish the changes in solution concentrations and surface fInish. Parameter maps were not able to distinguish between uniform and pitting corrosion of similar type of samples from different systems but were able to distinguish uniform corrosion from pitting corrosion. Cumulative probability method was not able to differentiate the variation in solution concentrations and in surface finish. It was also not able to distinguish between uniform and pitting corrosion. Impedance spectra analysis was not suitable to indicate the types of corrosion occurring. It was also unable to distinguish the variations in the solution concentrations and surface finishes used. Finally, it was found that, evolvement of corrosion parameters is independent of time.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available