Definition - 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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