Electrochemical Polarization Laboratory

This flashcard set covers the fundamental definitions, types of polarization, and kinetic parameters involved in electrochemical polarization and corrosion rate measurements as outlined in the laboratory manual.

Polarization

A change in electrode potential due to the flow of a current.

Overpotential ($\eta$)

The electrical potential difference between the polarized and the equilibrium (unpolarized) electrode potential.

Activation polarization

Polarization caused by a slow electrode reaction.

Concentration polarization

Polarization caused by concentration changes in reactants or products near an electrode surface.

Ohmic polarization

Polarization caused by IR drops in solution or across surface films, such as oxides (or salts).

Anodic Polarization

The displacement of the electrode potential in the positive direction, making the electrode act more anodic.

Cathodic Polarization

The displacement of the electrode potential in the negative direction, making the electrode act more cathodic.

Working Electrode (WE)

The electrode in an electrochemical cell whose potential is being changed or measured, such as the steel or copper coupons in this experiment.

Anodic Tafel slope ($\beta_a$)

The slope of the activation polarization curve for the anodic reaction, defined as $\beta_a = \frac{2.303RT}{\alpha zF}$.

Cathodic Tafel slope ($\beta_c$)

The slope of the activation polarization curve for the cathodic reaction, defined as $\beta_c = -\frac{2.303RT}{(1 - \alpha)zF}$.

Corrosion Potential ($E_{corr}$)

The potential at the point where the anodic and cathodic reaction curves intersect, identifying the potential where the anodic reaction rate equals the cathodic reaction rate.

Corrosion Current ($i_{corr}$)

The current density at the intersection of the anodic and cathodic reaction curves.

Polarization Resistance ($R_p$)

The slope of the $E - i$ curve, defined as $R_p = \frac{\Delta \eta}{\Delta i}$.

Symmetry coefficient ($\alpha$)

A kinetic parameter appearing in the Butler–Volmer equation and used to calculate Tafel slopes.

Faraday's Constant ($F$)

A constant used in the calculation of corrosion rate ($CR$), specified as $96494\,A \cdot s/mol$ in the laboratory data.

Density of Steel ($\rho_{st}$)

The specific mass per unit volume of steel used for experimental calculations, given as $7.8\,g\,cm^{-3}$.

Density of Copper ($\rho_{Cu}$)

The specific mass per unit volume of copper used for experimental calculations, given as $8.96\,g\,cm^{-3}$.

Atomic Weight of Iron ($A_{w, Fe}$)

The atomic weight used for carbon steel calculations, provided as $55.85\,g/mol$.

Atomic Weight of Copper ($A_{w, Cu}$)

The atomic weight used for copper calculations, provided as $63.55\,g/mol$.