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| DEGRADATION KINETICS OF PROTECTIVE COATING FOR ALUMINUM ALLOY |
| CAI Jianping1, LIU Ming1, AN Yinghui2 |
1. Department of Metal Corrosion and Protection, Beijing Institute of Aeronautical Materials, Beijing 100095
2. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 |
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Abstract The degradation process of polyamide epoxy varnish for aluminum alloy was studied in ultraviolet/ salt spray combined environmental test, the morphology of the coating was observed by environmental scanning electron microscopy(ESEM), other physical parameters such as volume resistance, surface resistance were also measured in the exposure test. Meanwhile, EIS(electrochemical impedance spectroscopy) was utilized to monitor degradation process of the coating. The results showed that the porosity of the coating increased and the volume resistance and surface resistance decreased in the degradation process. EIS illustrated different stages of the degradation process. First order type degradation kinetics or simplified KWW model are suggested and discussed based on the quantitative measurements; coating failure criterion determined from EIS was also suggested. It is considered that the electrical resistance and electrochemical impedance modulus at low frequency is suitable to construct degradation kinetics.
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Received: 11 April 2011
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Corresponding Authors:
CAI Jianping
E-mail: jpcai2001@yahoo.com.cn
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