Sunday, October 20, 2013

Galvanic Corrosion and Electrolysis in Saltwater Pools

When galvanic corrosion, electrolysis or staining occurs in saltwater pools, a SACRIFICIAL ANODE is not the placebo everyone is seeking. 

Marine Applications

On a boat, a sailor does not care if the anode erodes, or if the anode's metals dissolve into the water (ocean).  The anode on a boat is a lot cheaper than the wiring, prop or shaft.  It prevents the corrosion of the precious components, by SACRIFICING itself instead. 

Swimming Pool Application

But, placing a sacrificial anode in a swimming pool is doing the same thing as on a boat.  One is merely offering a SACRIFICIAL metal for the galvanic corrosion to attack, instead of the precious components. 

So instead of plating surfaces with copper, you will be plating them with zinc or magnesium from the anode.  The sacrificial anode will save the copper, but it will not stop the staining or plating of the stainless steel components.  That will NOW occur with the metal from the anode.  This is exactly why anodes need to be periodically replaced - they are sacrificed.

Sacrificial anodes are not the solution to the damage caused by galvanic corrosion or electrolysis.

Bonding Grid

The equipotential bonding grid does not prevent galvanic corrosion.  In fact, if there is stray voltage finding it's way to the pool through the property's CONTINUOUS GROUNDING SYSTEM, the equipotential bonding grid may actually be feeding voltage to the pool's metallic components. 

The bonding grid can actually function as either the electrode or cathode, depending if there is stray voltage present on the property, thereby energizing the bonding grid.  Alternatively, it can be providing a path to ground, where the equipotential bonding grid and the grounding grids are intentionally cross connected - pumps, heater's, panel boards, etc.

A Solution

For these very reasons, many pool builders that I know and I, have ceased installing salt systems.  We now promote the micro-dosing of bleach via a ORP/pH Controller, augmented by a commercial sized ozone generator and contact chamber.

Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: or 408-776-8220. 
 Visit his website at: 
All Contents © Aquatic Technology Pool & Spa, 2013. 
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To contact the author, Paolo Benedetti of Aquatic Technology pool and Spa, email him at: or call 408-776-8220.
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