Xingwen YU
,
Chuanwei YAN
,
Chunan CAO
材料科学技术（英文）
Technological process of rare earth sealing anodized LY12 (2024) alloy is introduced. Corrosion behavior of the film was studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that the coating remained passivity at the potential range from the open circuit potential (-780 mV) to –250 mV in NaCl solution. When the potential exceeded -200 mV, corrosion reaction happened on the coating. the results of EIS analysis was consistent with the results of polarization curves.
关键词:
LY12 alloy
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null
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null
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F.H. Cao
,
L. Guo
,
L.J. Zhang
,
Z. Zhang
,
J.Q. Zhang
金属学报(英文版)
The corrosion behavior of two different aged LY12 alloys in EXCO (234g/L NaCl, 50g/L KNO3, 0.1M HNO3) and MIL-H-600 (35g/L NaCl, 5g/L (NH4)2SO4) solutions were studied using electrochemical impedance spectroscopy (EIS) in conjunction with SEM technique respectively, and the pH variation of the above accelerated corrosion solution during materials corroding was also measured to characterize the corrosion processes. At the beginning of corrosion, EIS plots exhibited two capacitive arcs in the high frequency range (Cdl) and mediate frequency range (Clf) originating from the original corroded surface and the newly formed interface respectively, and a low frequency inductive loop due to the relaxation phenomenon of reaction intermediates. In the EXCO solution, the EIS results showed that once the exfoliation corrosion occurred, the inductive loop disappeared. The results also showed that the exfoliation corrosion susceptibility of state T6 is much higher than that of state T3, but the intergranular corrosion susceptibility has a reverse order. Based on the relationship of EIS results with SEM and metalloscopy morphologies of the corroding substrates and physic-chemical meaning of EIS parameters, an index (Clf / Cdl) has been proposed to characterize the extent of the localized corrosion, which variation tallies with the real corrosion extent correctly. Meanwhile, good agreement was found between the experimental results and the electrochemical model proposed and, good coherence between the electrochemical features and the distribution type of constituent particles of corroding material was observed.
关键词:
electrochemical impedance spectroscope
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null
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