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Electrochemical Corrosion Potential (ECP)

Definition - What does Electrochemical Corrosion Potential (ECP) mean?

Electrochemical corrosion potential (ECP) is the voltage difference between a metal immersed in a given environment and an appropriate standard reference electrode (SRE), or an electrode which has a stable and well-known electrode potential.

ECP is used to list metals or alloys based on their corrosion resistance.

Electrochemical corrosion potential is also known as rest potential, open circuit potential or freely corroding potential, and in equations it is represented by Ecorr.

Corrosionpedia explains Electrochemical Corrosion Potential (ECP)

When placed in an electrolyte, different metals or alloys corrode or react at different corrosion rates. The rate of corrosion of these metals depends on the corrosion potential of the metal. This potential can be measured by connecting the metal with an SRE and measuring the potential difference by using a voltmeter. The magnitude of the voltage and its sign are necessary for measuring and reporting corrosion potentials.

By using the galvanic series it is possible to construct a list of metals and alloys based on their relative corrosion potential in a given electrolyte. This is useful for predicting potential galvanic corrosion situations. The distance between two metals in the galvanic series gives an accurate indication of the magnitude of the driving force for corrosion. When two metals having greater distance in the series are connected in the electrochemical cell, there is a greater tendency for galvanic corrosion to occur.

Examples of SREs include:

  • Standard hydrogen electrode (SHE) (E = 0.000 V)
  • Normal hydrogen electrode (NHE) (E ˜ 0.000 V)
  • Reversible hydrogen electrode (RHE) (E = 0.000 V - 0.0591*pH)
  • Saturated calomel electrode (SCE) (E = +0.241 V saturated)
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