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Investigation of the calcareous deposits formation controlled by interfacial pH and its effect on the hydrogen entry into AISI 4135 steel in seawater |
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| Authors: | Yong Xu Yanliang Huang Dan Yang Hans Joerg Kunte Roland De Marco Xiutong Wang |
| Affiliation: | 1. CAS Key Laboratory of Marine Environment of Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, PR China;2. Open Studio for Marine Corrosion and Protection, Pilot National Laboratory for Marine Science and Technology, Qingdao, 266237, China;3. University of Chinese Academy of Sciences, Beijing, 100049, PR China;4. Center for Ocean Mega-Science, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071, PR China;5. Bundesanstalt für Materialforschung und –prüfung, Berlin, 12205, Germany;6. School of Science and Engineering, University of the Sunshine Coast, 90 Sippy Downs Drive, Queensland, 4556, Australia;7. Department of Chemistry, Curtin University, GPO Box U1987, Perth, Western Australia, 6109, Australia;8. School of Chemical and Molecular Biosciences, University of Queensland, Brisbane, Queensland 4072, Australia |
| Abstract: | The influence of interfacial pH between AISI 4135 steel and seawater under different polarization potentials on the formation of calcareous deposits has been studied. An interfacial pH of 9.61 at ?0.9 V vs. SCE using state of the art iridium oxide microelectrode was found to be the critical pH for the precipitation of magnesium hydroxide. Calcareous deposits with a double-layer structure comprising an inner-brucite layer and an outer-aragonite layer were found to form at potentials between ?1.0 V and ?1.2 V vs. SCE. Furthermore, the facilitation of hydrogen permeation into steel induced by the formation of calcareous deposits was verified using the Devanathan-Stachurski electrochemical test. The mechanism of calcareous deposits facilitates hydrogen permeation into steel is related to its inhibition on hydrogen recombination and escape processes. |
| Keywords: | Low alloy steel Cathodic protection Calcareous deposits Hydrogen permeation Interfacial pH |
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