A novel combination microelectrode was constructed based on an iridium pH microelectrode and an Ag/AgCl microelectrode, and was applied to simultaneously monitor the steel potential, pH and chloride ion concentration in a crevice simulating disbonding of pipeline coatings with cathodic protection (CP) applied or removed. The sensing characteristics and sensitivity of the microelectrode are described as well as the calibration procedures. A simulated crevice was formed between a pipeline steel surface and a polymethylmethacrylate plate. The results showed that in CP conditions, the evident potential gradient resulting from the IR potential drop was concentrated at the crevice opening. A protective local environment induced by CP under disbonded coatings was characterised by an increase in pH and removal of Cl(-). After CP is removed, the protective effects can persist for a period of time, depending on the diffusion of soluble species.
Electrochemical measurements using combination microelectrode in crevice simulating disbonded of pipeline coatings under cathodic protection
Elektrochemische Messungen mit zwei kombinierten Mikroelektroden an simulierten Fehlstellen (Spalt) von Pipeline-Beschichtungen bei kathodischem Schutz
Corrosion Engineering, Science and Technology ; 42 , 1 ; 42-49
2007
8 Seiten, 9 Bilder, 36 Quellen
Article (Journal)
English
Simulationsversuch , elektrochemische Überwachung , Korrosionsüberwachung , Pipeline , organischer Überzug , Polymethylacrylat , kathodischer Korrosionsschutz , Schutzschicht , Fehler , Spalt , elektrochemisches Untersuchungsverfahren , Mikroelektrode , simultanes Messverfahren , elektrochemisches Potenzial , pH-Wert , Konzentration , Potenzialverteilung , Spaltkorrosion
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