期刊
ANALYTICAL CHEMISTRY
卷 93, 期 28, 页码 9657-9662出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.analchem.1c01045
关键词
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资金
- National Research Council Canada (NRC)
- Centre quebecois de recherche et de developpement de l'aluminum (CQRDA)
The commonly used Ag/AgCl wire quasi-reference counter electrode in the quantitative scanning micropipette contact method may leak Ag+ into the electrolyte solution, leading to interference in potential and generation of faradaic current. By using a leak-free Ag/AgCl electrode or increasing the distance between the electrode and micropipette tip droplet, the contamination of Ag+ can be eliminated, allowing accurate measurement of corrosion potentials during oil-immersed scanning micropipette contact method measurements.
Quantitative scanning micropipette contact method measure- ments are subject to the deleterious effects of reference electrode interference. The commonly used Ag/AgCl wire quasi-reference counter electrode in the miniaturized electrochemical cell of the scanning micropipette contact method was found to leak Ag+ into the electrolyte solution. The reduction of these Ag+ species at the working electrode surface generates a faradaic current, which significantly affects the low magnitude currents inherently measured in the scanning micropipette contact method. We demonstrate that, during the microscopic corrosion investigation of the AA7075-T73 alloy using the oil-immersed scanning micropipette contact method, the cathodic current was increased by the Ag+ reduction, resulting in positive shifts of corrosion potentials. The use of a leak-free Ag/AgCl electrode or an extended distance between the Ag/AgCl wire and micropipette tip droplet eliminated the Ag+ contamination, making it possible to measure accurate corrosion potentials during the oil-immersed scanning micropipette contact method measurements.
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