Electrode Potential

Definition - What does Electrode Potential mean?

Electrode potential for any given electrode is the voltage or potential difference of a cell assembled from a standard hydrogen electrode and the given electrode with the potential that is being defined. It is the resultant potential difference between a point on the electrode surface and the point in the bulk of electrolyte, due to transfer of charged particles as well as the adsorption of some polar molecules.

As per convention, the standard hydrogen electrode is always at zero potential.

Electrode potential has uses such as:

  • Prediction of corrosion-related chemical or electrochemical reactions
  • Used for choosing substances and devices for controlling reactions
  • Helps the study of crevice corrosion and pitting, as electrode potential in crevices and pits is studied for controlling reactions

Corrosionpedia explains Electrode Potential

Electrode potential is useful as an indicator of likely reactions leading to corrosion. When it is within the protective potential range, then the protective system is considered effective.

Electrode potential depends on the direction of flow of electrons—whether the electrode is acting as the cathode or anode in its cell. It also depends on:

  • Electrolyte concentration
  • Temperature
  • Pressure

Oxidation and corrosion reaction on electrodes can be excessive, if there are continuously fluctuating voltages in the bulk electrolyte. The reaction rate can be controlled by using inhibitors and other techniques that help prevent oxidation reactions.

A popular technique is cathodic protection, which provides a passive layer across the surfaces, thus preventing direct access to corrosive reactants.

While studying pitting corrosion, electrode potential within surface cracks, pits and crevices is measured to determine the effectiveness of coatings and problems arising from holidays and surface defects.

Measurement of electrode potential requires the use of a standard reference electrode. The absolute electromotive force (EMF) or voltage of the electrode cannot be measured directly. After determining the potential of the standard electrode, other voltage measurements can be made against this standard reference electrode. If the reference electrode voltage is set to zero, the EMF measured can be treated as the absolute EMF of the cathode or anode.

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