How to Calculate and Solve for Concentration Polarization | Corrosion

The image of concentration polarization is shown below.

To compute for concentration polarization, six essential parameters are needed and these parameters are Gas Constant (R), Temperature (T), Number of Electrons (n), Faraday’s Constant (F), Current Density (i) and Limiting Diffusion Current Density (iL).

The formula for calculating concentration polarization:

ηc = 2.3RT/nF log(1 – i/iL)

Where:

ηc = Concentration Polarization
R = Gas Constant
T = Temperature
n = Number of Electrons
F = Faraday’s Constant
i = Current Density
iL = Limiting Diffusion Current Density

Let’s solve an example;
Find the concentration Polarization when the gas constant is 14, the temperature is 7, the number of electrons is 8, the faraday’s constant is 4, the current density is 1 and the limiting diffusion current density is 2.

This implies that;

R = Gas Constant = 14
T = Temperature = 7
n = Number of Electrons = 8
F = Faraday’s Constant = 4
i = Current Density = 1
iL = Limiting Diffusion Current Density = 2

ηc = 2.3RT/nF log(1 – i/iL)
ηc = 2.3(14)(7)/(8)(4) log(1 – (1/2))
ηc = 225.39/32 log(1 – 0.5)
ηc = 7.043749 log(0.5)
ηc = 7.043749 (-0.301029)
ηc = -2.120

Therefore, the concentration polarization is -2.120.

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