Galvanic Cell:

The system will be chemically unstable if there is a net conversion of reactants to products in a system, and the reaction will continue until a stable state is attained. That stable state is called as equilibrium.

An active electrochemical cell (oxidation-reduction reaction) is an unstable chemical system. A potential related along with a galvanic cell, for instance, steadily decreases as current flows and the oxidation-reduction reaction proceeds.  Eventually, the potential falls to zero; a cell no longer supplies electrical energy, and no additional net reaction takes place.  At this point the system is at equilibrium.  Within electrochemical cells, a decrease in cell potential caused through the operation of the cell (current flow) is known as polarization.

This modification in cell potential could be determined. Assume the zinc-copper galvanic cell display in Figure. As the reaction takes place, Zn⁺² ions (produced through the oxidation of zinc metal) pass into solution.  The Cu⁺² ions in solution are reduced as the copper metal plates out.  Therefore, the concentration of Zn⁺² in solution increases and the concentration of Cu⁺² decreases according to the following whole reaction.

Zn + Cu⁺² → Zn⁺² +Cu                                                        (1)

Figure:  A Galvanic Cell

Since Zn⁺² increases and Cu⁺² decreases then the electrical potential decreases.  This decrease in cell potential that gives output from changes within concentrations is one form of polarization known as concentration polarization.

Now assume a galvanic cell along with platinum and zinc electrodes, like as that display in Figure.  The half-reactions within the cell are given as follows.

Zn→ Zn⁺² +2e^-

H₃O⁺ + e^- → H+H₂O                                    (2)

Once more, as the cell operates a cell potential drop. The decrease is partially because of the increase in Zn⁺² concentrations and the decrease in H₃O⁺ concentration, other than another category of polarization also occurs within this cell. This second category is related along with the reduction half-reaction.