18
SALT IN POOL WATER AND GALVANIC CORROSION
ON AUTOMATIC SAFETY COVER SYSTEMS
“Galvanic corrosion tends to occur when dissimilar conducting materials are connected electrically and exposed to an electrolyte
(salt in water). “This can be a direct contact or secondary connection such as a common grounding path. ¹ An example of dissimilar
conducting materials is stainless-steel screws into aluminum. From 1962 to 1988, galvanic corrosion rarely occurred on aluminum
components of automatic covers.
Since 1999 when Underwriters Laboratories (UL) dictated that all metal components of automatic pool covers must be bonded to the
pool grid, we have seen an increase of galvanic corrosion on some of the aluminum components. In addition, the popularity of
electric chlorinators where salt is added to the pool water has increased.
These two changes in the industry are the reason you may experience galvanic corrosion on some aluminum components. In the past
it may have taken over 20 years for any noticeable corrosion. Today with bonded systems and salt water, reaction can occur within
two to three years.
The salt in the water acts as an electrolyte which is a non-metallic electric conductor. When removed from the pool, the cover will
deposit salt water on the mechanism end casting and main tube. If there are any “stray currents picked up” ² by the bonded pool grid,
galvanic corrosion can occuur starting where the stainless steel screws mount to the main tube and into the end casting. This
corrosion will appear as a black pitting and/or a powdery white dust. The white dust is not salt: It is aluminm that has oxidized.
Salt deposits may collect on parts such as guides and in the rope weave.
What maintenance can be done to reduce galvanic corrosion?
1. Several manufacturers of salt generators have indicated that there will be limited reaction to metals if the salt level is
maintained at levels below 3000-3200 ppm. They indicate that salt levels of 4500, 5500 ppm and above can be
corrosive even without the generator operating. Test the level and replace pool water if the salt levels are too high.
2. The mechanism should be washed down and brushed once a month is there is salt in the pool water. Spray down the
rope reels and end castings with fresh water; with a soft brush to loosen salt particles; and then hose down again.
3. On installations without a salt system, maintain a clean cover recess with twice a year rinsing of the cover
mechanism.
Salt in pool water and galvanic corrosion are not new to the industry. Salt generators were introduced over 25 years ago and those
that were in the industry at that time recall some of the concerns and problems in conjuction with heaters, pumps, filters, handrails and
light niches. Salt generators, like many other porducts, have positive and some negative factors; however, the most important
issue is to maintain proper water chemistry and salt levels. Salt generators are convenient for pool owners, although many tend to
neglect pH, alkalinity and salt levels. Regardless of the pool cover system, proper water chemistry is important to ensure the
maximum life of the pool and pool equipment:
Chorline levels: 1-5 ppm is a normal acceptable reading
Salt levels: per manuafacturers guidelines
PH levels: 7.2 - 7.8 ppm
Alkalinity levels: 80 - 120 ppm
The metal components of an Aquamatic Cover System are not warranted against galvanic corrosion created by salt water conditions;
this is not a manufacturer’s defect.
There is extensive information regarding galvanic corrosion on the internet.
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