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Apeldoorn, Netherlands

Homborg A.M.,Royal Netherlands Navy | Leon Morales C.F.,Endures BV | Tinga T.,Netherlands Defence Academy | De Wit J.H.W.,Technical University of Delft | Mol J.M.C.,Technical University of Delft
Electrochimica Acta | Year: 2014

This work investigates the electrochemical processes involved in pitting corrosion induced by microbiologically influenced corrosion by using time-resolved instantaneous frequency information of electrochemical current noise (ECN) transients obtained from Hilbert spectra. In addition to the time-frequency analyses, also the open corrosion potential is investigated and microscopic examinations of the specimens are performed after the tests. Hilbert spectra of the ECN signals indicated the development of transients in one of the two electrochemical cells containing sulphate-reducing bacteria with a different instantaneous frequency decomposition as compared to the background ECN signal, which resulted from the anaerobic general corrosion process. After day 13, the transients in the ECN signals developed towards consistent instantaneous frequency decompositions in the Hilbert spectra that are typical for relatively fast pitting corrosion processes. Post-exposure microscopic observations confirmed the existence of pits underneath the attached biofilms at the working electrodes. © 2014 Elsevier Ltd. Source

Homborg A.M.,Royal Netherlands Navy | Tinga T.,Netherlands Defence Academy | Van Westing E.P.M.,Tata Steel | Zhang X.,Endures BV | And 3 more authors.
Corrosion | Year: 2014

In this paper, procedures and parameters that enable identification of, or discrimination between, general and localized corrosion processes through electrochemical noise are critically discussed. Their relevant similarities, differences, and interdependences are indicated. In addition, the relation between different procedures and parameters with the underlying physico-chemical processes is indicated. Consistent and reliable information can be obtained from electrochemical noise data when a data analysis procedure is selected, which on the one hand has a high discrimination ability and on the other hand yields a descriptive parameter that is directly associated to the underlying physico-chemical process. Procedures that meet these two requirements appear to be the Hilbert-Huang transform (Hilbert spectrum), wavelet transform (energy distribution plot), and the analysis of charge and frequency of corrosion events. In addition to the procedures that meet these two requirements, some of the descriptive parameters can be determined by different analysis procedures, which increase their reliability. © 2014, NACE International. Source

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