期刊
JOURNAL OF OCEAN UNIVERSITY OF CHINA
卷 16, 期 2, 页码 243-248出版社
OCEAN UNIV CHINA
DOI: 10.1007/s11802-017-2933-4
关键词
seawater; calcareous deposits; dissolved oxygen; galvanostatic; cathodic protection
类别
资金
- National Basic Research Program of China (973 Project) [2014CB643300]
- National Environmental Corrosion Platform (NECP)
The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied. When the dissolved oxygen concentration was less than 7 mg L-1, the cathodic protection potential showed a plateau at the initial polarization, and then quickly shifted negatively. While the dissolved oxygen was more than 9 mg L-1, the potential shifted negatively in a linear form. After 168 h of polarization, the final protection potential shifted negatively with the decreasing dissolved oxygen concentration. The deposition progress was monitored by electrochemical impedance spectroscopy, and only one single loop was found in Nyquist diagram, indicating deposits of ineffective protectiveness precipitation under the experimental conditions. The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique. The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration, such as 1 mg L-1, resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor. Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions, and that dissolved oxygen had no effect on the crystalline types of calcium carbonate.
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