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Last updated: July 19, 2024

What Does POH Mean?

pOH is a measure of the hydroxide ion (OH) concentration of a solution. As such, it can be used as an indicator of a substance’s alkalinity or even its electrical conductivity in some cases. More specifically, pOH is the negative logarithm of the hydroxide ion content given by the expression:

pOH = 14 – pH


Corrosionpedia Explains POH

The concentration of hydroxide ions in a solution is related to the concentration of hydrogen ions by the expression:

OH = Kw/OH+

Where Kw = self-ionization content of water.

Applying logarithms on both sides, the more common form of the equation is expressed as shown below:

pOH = pKw – pH

Therefore, at room temperature, pOH can be expressed as:

pOH = 14 – pH

In terms of corrosion, pOH can be used as an indicator of an electrolyte’s conductivity in a galvanic cell. The conductivity of a solution is dependent on the concentration of ions that act as charge carriers. Therefore, the larger the concentration of OH ions, the stronger the alkalinity, the higher the electrolyte’s conductivity, and therefore the higher the rate of galvanic corrosion.


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