Phosphate SWCG inhibition

Aqua Lab Rat

In The Industry
May 1, 2015
124
Anoka, MN
I've been doing some reading about the various types of phosphates and their use in water supplies. This Link says in its section titled "The Functions of Orthophosphates/Polyphosphates" that Ortho is an anodic inhibitor and Poly is a cathodic inhibitor, when talking about electro-chemical corrosion. I was wondering whether these characteristics might come into play with SWCG output. My instinct is to say that the power output of a SWCG is so much greater than a corrosion cell that I'm probably just going down a rabbit hole. But I thought I'd mention it anyway.
 
It’s not the same concept. Chemical Corrosion inhibitors refer to galvanic corrosion of dissimilar metal surfaces in contact with one another. So an anodic inhibitor refers to a chemical species that inhibits the oxidation of a metal atom, ie, the inhibitor prevents the metal atom from giving up an electron and thus becoming more soluble. A cathodic inhibitor blocks the reduction of a metal ion in solution at the surface by inhibiting the acceptance of an electron. This would prevent the build up of a metal scale. When used in conjunction, the chemicals inhibit the galvanic corrosion of iron, copper, and lead in old pipes that would cause water quality problems.

That use of those chemicals is distinct from what goes on in an SWG cell (electrolysis of brine) and would not necessarily create the same effect since the SWG cell is oxidizing chloride ions to chlorine and reducing water to hydrogen gas and hydroxyl ions. There would have to be a mechanism by which the orthophosphate competitively interferes with the oxidation of chloride and that’s not really seen. Also, when one looks at the concentrations involved, the amount of ortho-/polyphosphates used is an order of magnitude higher than what’s seen in pool water.

It’s a rabbit hole ...
 
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