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.