## 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.

## How to Calculate and Solve for Current Density | Electrical Properties

The current density is illustrated by the image below.

To compute for current density, two essential parameters are needed and the parameters are Electrical Conductivity (σ) and Electric Field Intensity (E).

The formula for calculating current density:

j = σE

Where:

j = Current Density
σ = Electrical Conductivity
E = Electric Field Intensity

Let’s solve an example;
Find the current density when the electrical conductivity is 32 and the electric field intensity is 4.

This implies that;

σ = Electrical Conductivity = 32
E = Electric Field Intensity = 4

j = σE
j = (32)(4)
j = 128

Therefore, the current density is 128 A/m².

## How to Calculate and Solve for Exchange Current Density | Corrosion

The exchange current density is illustrated by the image below.

To compute for exchange current density, three essential parameters are needed and these parameters are Current Density (io), Number of Electrons (n) and Faraday’s Constant (F).

The formula for calculating exchange current density:

γredoxid) = io/nF

Where:

γredoxid) = Exhange Current Density
io = Current Density
n = Number of Electrons
F = Faraday’s Constant

Given an example;
Find the exchange current density when the current density is 8, the number of electrons is 4 and the faraday’s constant is 2.

This implies that;

io = Current Density = 8
n = Number of Electrons = 4
F = Faraday’s Constant = 2

γredoxid) = io/nF
γredoxid) = 8/(4)(2)
γredoxid) = 8/(8)
γredoxid) = 1

Therefore, the exchange current density is 1.