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| DETERMINATION OF INSTANTANEOUS CORROSION RATE BY HARMONIC ANALYSIS Ⅰ.POWER SERIES EXPANSION |
| Xu Naixin(Shanghai Institute of Metallurgy. Academia Sinica) J. L. Dawson G. E. Thompson G. C. Wood(Corrosion and Protection Center; UMIST) |
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Abstract The conventional a.c.impedance technique only provides polarization resistance inversely proportional to the corrosion rate. The proportionality constant has to be determined in an independent experiment. However, the harmonic components appearing in a.c. impedance measurments reflect nonlinear polarization characteristics of the corrosion system under study. By means of barmonic analysis, corrosion current could be obtained directly and Tafel slopes could be determined simultaneously. In the present paper, the basic formulas based on power series expansion for manipulation of harmonic data are derired. Mild steel corroding in 0.5N H_2SO_4 was chosen for experimental verification. The first three harmonic components are measured by a frequency response analyzer with harmonic selector. The measured data have been corrected for IR drop due to solution resistance. The shunting effect of the double layer capacitance has also been eliminated by subtracting the capacitive current from the first harmonic component. The effect of frequency of a. c. signal is discussed. The results show that corrosion rate determined by harmonic analysis correlates well with those from a.c. impedance and weight loss measurements. Tafel slopes obtained are in good agreement with those measured from polarization curves.
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Received: 25 June 1984
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Cite this article:
Xu Naixin(Shanghai Institute of Metallurgy. Academia Sinica) J. L. Dawson G. E. Thompson G. C. Wood(Corrosion and Protection Center; UMIST). DETERMINATION OF INSTANTANEOUS CORROSION RATE BY HARMONIC ANALYSIS Ⅰ.POWER SERIES EXPANSION. J Chin Soc Corr Pro, 1984, 4(3): 159-166.
URL:
https://www.jcscp.org/EN/ OR https://www.jcscp.org/EN/Y1984/V4/I3/159
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[1] Devanathan, M. A. V. Electrochimica Acta, 17, 1755(1972)
[2] Prabhakara Rao, G. Mishra, A. K. J. Electroanal. Chem,77, 121(1977)
[3] Devay, J. Meszaros, L. Acta Chimica Academiae Scientiarum, Hungaricae, 100, 183(1979)
[4] Devay, J. Meszaros, L. ibid,104, 311(1980) |
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