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Abstract No matter what kind of localized corrosion cell it is, there is always a potential difference between its cathode and occluded anode. There are actual ly a few components in the potential difference between the cathode and the anode in localized corrosion cell. The character of one of its important components-diffusion potential difference—is analyzed theoretically. For measuring its value, a device is designed to simulate the main structural characteristics of the cell. For the localized corrosion system of iron in 10~(-3)N NaCl solution, along with the propagation of the localized corrosion, the concentration of FeCl_2 in anolyte will increase gradually. In such a case, this diffusion potential difference is linear with the logarithm of the concentration of FeCl_2 in anolyte. At 20℃, it will increase 32mV for each ten-fold of the increase of the concentration of FeCl_2. When the anolyte changes to saturated solution in FeCl_2, it equals 125±2 mV. The results measured experimentally are well coincided with the values calculated theoretically based on the Planck-Henderson's equation. The results prove that, this diffusion potential difference is a nonequilibrium potential difference caused by the difference of the ionic mobilities or the difference of the diffusion coefficients of all ions of both the occluded anolyte and the bulk solution. For Cl~- containing solution, it does not equal the potential difference between two equilibrium electrodes reversible to Cl~- in the anolyte and in the bulk solution respectively.
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Received: 25 April 1984
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[1] Pickering, H.W.; Frankenthal, R.P., J. Electrochem. Soc., 119, 1297(1972)
[2] pourbaix, M., CEBELCOR, Rapports Techniques, 111, RT.166(1969)
[3] Alkire, R.; Ernsberger, D., Damon, D., J. Electrochem.Soc., 123, 458(1976)
[4] Schwenk, W., Corrosion, 20, 129t(1964)
[5] Nisancioglu, K.; Holtan, H., Electrochim. Acta, 23, 3, 251～3 (1978)
[6] Galvele, J.R., J. Electrochem. Soc., 123, 464(1976)
[7] Pourbaix, M., Occlusion corrosion cells and crack tip chemistry. Lecture delivered at the NATO Advanced Research Institute ATOMISTICS OF FRACTURE, 22～31 May, 1981, San Sebastiao(Corsica)
[8] Bockris, J. O'M.; Reddy, A. K. N., Modern Electrochemistry. 1, p.408, Plenum Press, New York(1970)
[9] Planck, M., Ann. Physik.,39, 161(1890a); ibid., 40, 561(1890b); or cf. Bockris, J.O'M.; Fredlein, R. A., "A Workbook of Electrochemistry", p.38～40, Plenum Press, New York-London(1973)
[10] Henderson, P., Z. Physik.Chem, 59, 118(1907) ; ibid., 63, 325(1908)
[11] Sathler, L.; Van Muylder, J.; Winand, R.; Pourbaix, M., Proce. edings of the 7th International Congress on Metallic Corrosion, 705(1978)
[12] Parsons, R., Handbook of Electrochemical Constants, (1959)
[13] Sathler, L., Contribution a l'etude du comportment electrochimique du fer en presence de solutions de chlorure ferreux, en liaison avec corrosion localisee. These de Doctorat, (1978) , Universite Libre de Bruxelles, p.164
[14] International Critical Tables. 6, p.309 |
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