Faraday's Law

Definition - What does Faraday's Law mean?

Faraday’s law was discovered by Michael Faraday, one of the pioneers in electrochemistry during the 19th century. This law states that when current produced by anodic areas are known, it is possible to calculate the rate of corrosion penetration or corresponding mass loss.

This law relates to electrolysis and how the electrochemical reaction current is associated with the moles of elements under reaction.

Corrosionpedia explains Faraday's Law

Faraday’s law is used to compute corrosion rates according to the kinetics of the cathodic and anodic reactions or the oxidation-reduction. Based on this empirical law, a linear relationship exists between the rate of corrosion or metal dissolution and the corrosion current. This can be expressed in the following equation:

    *RM = M/nFP (icorr)


    RM = Corrosion rate
    Icorr = Corrosion current
    M = Atomic weight of metal
    p = Density
    n = Charge number that indicates electrons exchanged within dissolution reaction
    F = Faraday constant equivalent to 96.485 C/mol
    M/n = Equivalent weight

In order to determine the rate of corrosion, the corrosion currents should be determined. This is possible when the reaction mechanisms involving corrosion reactions are also identified. Tafel slope analysis can help calculate corrosion currents. With this, the Tafel plot is used to perform analysis of the currents.

Using Faraday's law along with the Tafel plot, industries are able to predict whether a certain setup is likely to lead to corrosion. It also notes how fast the rate of corrosion will be in a given setup, making this law significant in corrosion testing and prevention.

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