# Partial current

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In [electrochemistry](/source/electrochemistry), '''partial current''' is defined as the [electric current](/source/electric_current) associated with ([anodic](/source/anode) or [cathodic](/source/cathode)) half of the [electrode](/source/electrode) [reaction](/source/chemical_reaction).

Depending on the electrode half-reaction, one can distinguish two types of partial current:
* '''cathodic partial current''' ''I<sub>c</sub>'' (called also '''cathodic current'''): is the flow of [electrons](/source/electrons) from the electrode surface to a species in solution;
* '''anodic partial current''' ''I<sub>a</sub>'' (called also '''anodic current'''): is the flow of electrons into the electrode from a species in solution.

The cathodic and anodic partial currents are defined by [IUPAC](/source/IUPAC).<ref name="iupac">{{GoldBookRef |title=partial anodic (cathodic) current |file=P04407 }}</ref>

The '''partial [current densities](/source/Current_density)''' (''i<sub>c</sub>'' and ''i<sub>a</sub>'') are the ratios of partial currents respect to the electrode areas (''A<sub>c</sub>'' and ''A<sub>a</sub>''):

:''i<sub>c</sub> = I<sub>c</sub>/A<sub>c</sub>''
:''i<sub>a</sub> = I<sub>a</sub>/A<sub>a</sub>''

The sum of the cathodic partial current density ''i<sub>c</sub>'' (positive) and the anodic partial current density ''i<sub>a</sub>'' (negative) gives the [net current density](/source/net_current_density) ''i'':<ref name=cwru>[http://electrochem.cwru.edu/ed/dict.htm Electrochemistry Dictionary and Encyclopedia] {{webarchive|url=http://webarchive.loc.gov/all/20011125103514/http%3A//electrochem.cwru.edu/ed/dict.htm |date=2001-11-25 }}</ref>

:''i = i<sub>c</sub> + i<sub>a</sub>''

In the case of the cathodic partial current density being equal to the anodic partial current density (for example, in a [corrosion](/source/corrosion) process<ref>B. Elsener, [http://www.surface.mat.ethz.ch/education/courses/surfaces_and_interfaces/chapter11 ''Corrosion and durability of metals''] {{webarchive|url=https://web.archive.org/web/20120918210609/http://www.surface.mat.ethz.ch/education/courses/surfaces_and_interfaces/chapter11 |date=2012-09-18 }} , p. 252.</ref>), the net current density on the electrode is zero:<ref name=cwru/>

:''i<sub>eq</sub> = i<sub>c,eq</sub> + i<sub>a,eq</sub> = 0''

When more than one reaction occur on an electrode simultaneously, then the total electrode current can be expressed as:<ref name="iupac"/>

:<math>I = \Sigma I_{a,j} + \Sigma I_{c,j}</math>

where the index ''<math>j</math>'' refers to the particular reactions.

==Notes==
<references/>

== References ==
* Bard, A.J. and Faulkner L.R. ''Electrochemical Methods: Fundamentals and Applications'' (2nd ed.), 2001 John Wiley & Sons Inc.

==See also==
* [Exchange current density](/source/Exchange_current_density)

Category:Electrochemistry

{{electrochem-stub}}

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Adapted from the Wikipedia article [Partial current](https://en.wikipedia.org/wiki/Partial_current) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Partial_current?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.