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| Corrosion & Environmental Degradation |
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When
reactions at the electrode are controlled by electrolytic diffusion processes,
different overpotential-log i curves are obtained in reduction.
· The flux, J, of species to the cathode is governed by Fick's first law: J = - D(T) (dc/dx) where (dc/dx) the species concentration gradient in the steady state. · If an applied overpotential is increased from zero, the current initially increases, but then reaches a limiting value, iL, determined by the diffusion flux. · The curve shown is related to the over- potential by: ηC = 2.3(RT/nF) log10{1 - (i/iL)} with, R, the Gas Constant and, F, Faraday's constant. This form assumes that no activation processes occur at the electrodes and that the electrolyte is static. |
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| From:
M.G. Fontana,
"Corrosion Engineering," Wiley (1986) |
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